hst physical science teachers editions5ebeba82addad021.jimcontent.com/download/version/...crf...

UNIT

T I M E L I N E

4

The AtomThousands of years ago, people began asking the question, “What is matter made of?” This unit follows the discoveries and ideas that have led to our current theories about what makes up matter. You will learn about the atom—the build-ing block of all matter—and its structure. You will also learn how the periodic table is used to classify and organize elements according to patterns in atomic structure and other properties. This timeline illustrates some of the events that have brought us to our current under-standing of atoms and of the periodic table in which they are organized.

308 Unit 4

Around400 BCE

The Greek philosopher

Democritus proposes

that small particles

called atoms make up

all matter.

1911Ernest Rutherford, a

physicist from New

Zealand, discovers

the positively

charged nucleus

of the atom.

1981Scientists in Switzerland

develop a scanning

tunneling microscope,

which is used to see

atoms for the first time.

1897British scientist J.J.

Thomson identifies

electrons as particles

that are present in

every atom.

The Atom 309

1932The neutron, one of the

particles in the nucleus

of an atom, is discovered

by British physicist James

Chadwick.

1989Germans celebrate when the

Berlin Wall ceases to function

as a barrier between East and

West Germany.

1803British scientist and

school teacher John

Dalton reintroduces

the concept of atoms

with evidence to

support his ideas.

1869Russian chemist Dmitri

Mendeleev develops

a periodic table that

organizes the elements

known at the time.

1945The United Nations is

formed. Its purpose

is to maintain world

peace and develop

friendly relations

between countries.

1996Another element

is added to the

periodic table after

a team of German

scientists synthesize

an atom containing

112 protons in

its nucleus.

2001Researchers use electron

beam technology to

create a tiny silicon

transistor that is only

80 atoms wide and that

can run at speeds of

almost 20 gigahertz.

James Marshall finds

gold while building

Sutter’s Mill, starting

the California gold rush.

1848

OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

Compression guide:To shorten instructionbecause of time limitations,omit the Chapter Lab.

11 Introduction to AtomsChapter Planning Guide

Chapter Opener

309A Chapter 11 • Introduction to Atoms

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P45 Thomson’s Cathode-Ray Tube

Experiment* TR P46 Rutherford’s Gold-Foil

Experiment*CD Science Tutor

TE Activity Photographic Dots, p. 312g TE Activity Scientist Flashcards, p. 313b TE Connection Activity Math, p. 314g TE Connection Activity Literature, p. 315g LB Whiz-Bang Demonstrations As a Matter of

Space*b

Section 1 Development of the Atomic Theory• Describe some of the experiments that led to the

current atomic theory.• Compare the different models of the atom.• Explain how the atomic theory has changed as

scientists have discovered new information aboutthe atom.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P47 Parts of an Atom* TR P48 Forces in the Atom* TR LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E87 Fusion of

Hydrogen in the Sun* SE Internet Activity, p. 321g

CRF SciLinks Activity*gVID Lab Videos for Physical ScienceCD Science Tutor

TE Connection Activity Real World, p. 319g SE School-to-Home Activity Atomic Diagrams,

p. 322g TE Connection Activity Life Science, p. 322g TE Activity Reconstructing Atoms, p. 322g TE Connection Activity Math, p. 323g SE Model-Making Lab Made to Order, p. 326g

CRF Datasheet for Chapter Lab* LB Whiz-Bang Demonstrations Candy Lights*g LB Long-Term Projects & Research Ideas How Low Can

They Go?a SE Science in Action Math, Social Studies, and Language

Arts Activities, pp. 332–333g

PACING • 90 min pp. 318–325Section 2 The Atom• Describe the size of the atom.• Name the parts of an atom.• Describe the relationship between numbers of

protons and neutrons and atomic number.• State how isotopes differ.• Calculate atomic masses.• Describe the forces within an atom.

OSP Parent Letter ■

CD Student Edition on CD-ROM CD Guided Reading Audio CD ■

TR Chapter Starter Transparency*VID Brain Food Video Quiz

SE Start-up Activity, p. 311gpp. 310–317PACING • 90 min

CRF Vocabulary Activity*g SE Chapter Review, pp. 328–329g

CRF Chapter Review* ■g

CRF Chapter Tests A* ■g, B*a, C*s SE Standardized Test Preparation, pp. 330–331g

CRF Standardized Test Preparation*gCRF Performance-Based Assessment*gOSP Test Generator, Test Item Listing

CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION

PACING • 90 min

Online and Technology Resources

Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HP7 Homefor a variety of freeonline resources.

This CD-ROM package includes:• Lab Materials QuickList Software• Holt Calendar Planner• Customizable Lesson Plans• Printable Worksheets

• ExamView® Test Generator• Interactive Teacher’s Edition• Holt PuzzlePro®

• Holt PowerPoint® Resources

STANDARDS CORRELATION SKILLS DEVELOPMENT RESOURCES SECTION REVIEW AND ASSESSMENT CORRELATIONS

Chapter 11 • Chapter Planning Guide 309B

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Reading Organizer, p. 312g TE Support for English Language Learners, p. 313 SE Connection to Language Arts Solving Mysteries, p. 315g TE Inclusion Strategies, p. 315

CRF Reinforcement Worksheet Atomic Timeline*b MS Math Skills for Science Using Proportions and Cross-Multiplication*g

SE Reading Checks, pp. 313, 315, 316g TE Homework, p. 315g TE Reteaching, p. 316b TE Quiz, p. 316g TE Alternative Assessment, p. 316g SE Section Review,* p. 317 ■g

CRF Section Quiz* ■g

UCP 2; SAI 2; HNS 1, 2, 3

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Reading Organizer, p. 318g TE Reading Strategy Atomic Diagrams, p. 319g SE Connection to Astronomy Hydrogen, p. 320g TE Inclusion Strategies, p. 321 TE Support for English Language Learners, p. 321 SE Math Focus Atomic Mass, p. 323g MS Math Skills for Science Arithmetic with Decimals*gCRF Critical Thinking Incredible Shrinking Scientist!*a

SE Reading Checks, pp. 319, 320, 322, 324g TE Reteaching, p. 324b TE Quiz, p. 324g TE Alternative Assessment, p. 324g SE Section Review,* p. 325 ■g

CRF Section Quiz* ■g

PS 1cChapter Lab SAI 1

SE Pre-Reading Activity, p. 310gOSP Science Puzzlers, Twisters & Teasersg

National ScienceEducation Standards

SAI 1, 2

CRF Chapter Resource File SS Science Skills Worksheets IT Interactive TextbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner

SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish

KEY

Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.

www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HP5CS11T.

• Lab Videos demonstratethe chapter lab.

• Brain Food Video Quizzeshelp students review thechapter material.

ClassroomVideos

Holt Lab GeneratorCD-ROM

Search for any lab by topic, standard,difficulty level, or time. Edit any labto fit your needs, or create your ownlabs. Use the Lab Materials QuickListsoftware to customize your labmaterials list.

• Guided Reading Audio CD(Also in Spanish)

• Interactive Explorations• Virtual Investigations• Visual Concepts• Science Tutor

ClassroomCD-ROMs

Planning ResourcesTEST ITEM LISTINGPARENT LETTERLESSON PLANS

Visual ResourcesCHAPTER STARTER

TRANSPARENCYBELLRINGER

TRANSPARENCIES

CONCEPT MAPPING TRANSPARENCYTEACHING TRANSPARENCIES

TEACHING TRANSPARENCIES

TEST ITEM LISTING

Copyright © by Holt Rinehart and Winston All rights reserved

The World of ScienceMULTIPLE CHOICE

1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2

2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2

3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1

4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2

5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2

6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2

7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2

8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2

9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2

10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2

TEACHER RESOURCE PAGE

Lesson Plan

Section: Waves

PacingRegular Schedule: with lab(s): 2 days without lab(s): 2 days

Block Schedule: with lab(s): 1 1/2 days without lab(s): 1 day

Objectives1. Relate the seven properties of life to a living organism.

2. Describe seven themes that can help you to organize what you learn aboutbiology.

3. Identify the tiny structures that make up all living organisms.

4. Differentiate between reproduction and heredity and between metabolismand homeostasis.

National Science Education Standards CoveredLSInter6: Cells have particular structures that underlie their functions.

LSMat1: Most cell functions involve chemical reactions.

LSBeh1:Cells store and use information to guide their functions.

UCP1:Cell functions are regulated.

SI1: Cells can differentiate and form complete multicellular organisms.

PS1: Species evolve over time.

ESS1: The great diversity of organisms is the result of more than 3.5 billion yearsof evolution.

ESS2: Natural selection and its evolutionary consequences provide a scientificexplanation for the fossil record of ancient life forms as well as for the strikingmolecular similarities observed among the diverse species of living organisms.

ST1: The millions of different species of plants, animals, and microorganismsthat live on Earth today are related by descent from common ancestors.

ST2: The energy for life primarily comes from the sun.

SPSP1: The complexity and organization of organisms accommodates the needfor obtaining, transforming, transporting, releasing, and eliminating the matterand energy used to sustain the organism.

SPSP6: As matter and energy flows through different levels of organization ofliving systems—cells, organs, communities—and between living systems and thephysical environment, chemical elements are recombined in different ways.

HNS1: Organisms have behavioral responses to internal changes and to externalstimuli.

This CD-ROM includes all of the resources shown here and the following time-saving tools:

• Lab Materials QuickList Software

• Customizable lesson plans

• Holt Calendar Planner

• The powerful ExamView ® Test Generator

Chapter Resources

Dear Parent,

Your son's or daughter's science class will soon begin exploring the chapter entitled “The

World of Physical Science.” In this chapter, students will learn about how the scientific

method applies to the world of physical science and the role of physical science in the

world. By the end of the chapter, students should demonstrate a clear understanding of the

chapter’s main ideas and be able to discuss the following topics:

1. physical science as the study of energy and matter (Section 1)

2. the role of physical science in the world around them (Section 1)

3. careers that rely on physical science (Section 1)

4. the steps used in the scientific method (Section 2)

5. examples of technology (Section 2)

6. how the scientific method is used to answer questions and solve problems (Section 2)

7. how our knowledge of science changes over time (Section 2)

8. how models represent real objects or systems (Section 3)

9. examples of different ways models are used in science (Section 3)

10. the importance of the International System of Units (Section 4)

11. the appropriate units to use for particular measurements (Section 4)

12. how area and density are derived quantities (Section 4)

Questions to Ask Along the Way

You can help your son or daughter learn about these topics by asking interesting questions

such as the following:

• What are some surprising careers that use physical science?

• What is a characteristic of a good hypothesis?

• When is it a good idea to use a model?

• Why do Americans measure things in terms of inches and yards instead of centimeters

and meters ?

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Form

ation

of th

e Solar System

TEACH

ING

TRA

NSPA

REN

CY

Fusion of Hydrogen in the Sun

Deu

terium

Two hydrogen

nuclei (protons) collide. One

proton emits particles and

energy and then becomes

a neutron. The proton and neutron com

bine to produce a heavy form

of hydrogen called

deuterium.

Heliu

m-3

Deuterium

combines w

ith another hydrogen nucleus to form

a variety of helium

called helium

-3. More energy,

as well as gam

ma rays,

is released.

Heliu

m-4 Tw

o helium-3

atoms then com

bine to form

ordinary helium-

4, which releases m

ore energy and a pair of hydrogen nuclei.

Hydrogen

Gam

ma ray

12

3

309C Chapter 11 • Introduction to Atoms

11

Chapter: Formation of the Solar System

Would YouBelieve . . . ?

Introduction to Atoms CHAPTER STARTER

Tiny atoms have something in commonwith huge dinosaurs. In both cases, scientists have had to try to under-stand something they could not observefirsthand!

No one has ever seen a livingdinosaur, but scientists have determinedthe appearance of Tyrannosaurus rex bystudying fossilized skeletons. Scientiststheorize that these now-extinct creatureshad big hind legs, small front legs, a long, whip-like tail, and a mouth full ofdagger-shaped teeth.

However, theories of how T. rexwalked have been harder to develop. Formany years, most scientists thought thatT. rex plodded slowly like a big, lazylizard. However, after studying well-preserved dinosaur tracks, like thoseshown below, and noticing skeletal sim-ilarities between certain dinosaur fossilsand living creatures such as the ostrich,many scientists now theorize that T. rexcould turn on the speed. Some scientistsestimate that T. rex had bursts of speedof 32 km/h (20 mi/h)!

Theories about T. rex and otherdinosaurs have changed gradually basedon indirect evidence, such as dinosaurtracks. Likewise, our theory of the atomhas changed as scientists have uncoveredmore evidence about the atom, eventhough they were unable to see an atomdirectly. In this chapter, you’ll learn aboutthe development of the atomic theoryand our current understanding of atomicstructure.


Introduction to Atoms BELLRINGER TRANSPARENCY


Section: Development of the Atomic TheoryThe following is a quote by Democritus (c. 460–c. 370 BCE). Paraphrase this quote in your own wordsin your science journal.

“Color exists by convention, sweet by convention,bitter by convention; in reality nothing exists butatoms and the void.”

What do you know about Democritus? And why arehis thoughts important?

Section: The AtomAnswer the following question:

An atom is the smallest particle into which anelement can be divided and still be that element.Now that scientists have learned that an atom ismade up of even smaller particles, is this definitionstill accurate?

Explain your answer in your science journal.


Intro

du

ction

to A

tom

sTEA

CHIN

G TR

AN

SPAR

ENCY

Thomson’s Cathode-Ray Tube Experim

ent

–+

When the plates w

ere charged, the beam

pro-duced a glow

ing spot here after being pulled tow

ard the positively charged plate.

Metal plates could be

charged to change the path of the beam

.

When the plates w

ere not charged, the beam

made

a glowing spot here.

Alm

ost all gas was rem

oved from

the glass tube.

An invisible beam

w

asproduced w

hen the tube w

as con-nected to a source of electrical energy.

yp

e

ab

c

d


Intro

du

ction

to A

tom

sTEA

CHIN

G TR

AN

SPAR

ENCY

Parts of an Atom

Pro

ton

s are positively charged par-ticles in the nucleus of an atom

.

Neu

tron

s are particles in the nucleus of an atom

that have no charge.

Electron

s are negatively charged particles found in electron clouds outside the nucleus. The size of the electron clouds determ

ines the size of the atom.

The nu

cleus is the

small, dense, positively

charged center of the atom

. It contains most

of the atom’s m

ass.

The diameter of the

nucleus is 1/100,000 the diam

eter of the atom.


Intro

du

ction

to A

tom

sTEA

CHIN

G TR

AN

SPAR

ENCY

Rutherford’s Gold-Foil Experiment

A few

particles bounced straight back.

e

Some particles w

ere slightly deflected from

a straight path.

d

An elem

ent such as radium

produced the particles.

a

Lead stopped all of the positive particles except for a sm

all stream

aimed at a gold-foil target.

b

Most of the

particles passed straight through the gold foil.

c

Forces in the AtomIntroduction to Atoms TEACHING TRANSPARENCY


Weak Force The weak force is an important force in radioac-tive atoms. In certain unstable atoms, a neutron can change into a proton and an electron. The weak force plays a key role in this change.

Strong Force Protons push away from one another because of the electromagnetic force. A nucleus containing two or more protons would fly apart if it were not for the strongforce. At the close distances between protons and neutrons in the nucleus, the strong force is greater than the electromag-netic force, so the nucleus stays together.

Electromagnetic Force As men-tioned earlier, objects that have the same charge repel each other, while objects with opposite charge attract each other. This is due to the electromagneticforce. Protons and electrons are attracted to each other because they have opposite charges. The electromagnetic force holds the electrons around the nucleus.

Gravitational Force Probably the most familiar of the four forces is gravitational force. Gravitational force acts between all objects all the time. The amount of gravitational force between objects depends on their masses and the distance between them. Gravitational force pulls objects, such as the sun, Earth, cars, and books, toward one another. However, because the masses of particles in atoms are so small, the gravitational force within atoms is very small.

Particles with the same charges repel each other.

F tom

Particles with opposite charges attract each other.

neutrons

whose numbers added together

make the

composed of

which identifies

are made up of

whose number is called the

Introduction to Atoms CONCEPT MAPPING TRANSPARENCY


Use the following terms to complete the concept map below:a nucleus, mass number, isotopes, protons, atoms, electrons,atomic number

SAMPLE SAMPLE SAMPLE

Meeting Individual Needs

Review and Assessments

Labs and Activities

DIRECTED READING A VOCABULARY ACTIVITY REINFORCEMENT

DATASHEETS FOR QUICKLABS

DATASHEETS FOR QUICK LABS

STANDARDIZED TEST PREPARATIONCHAPTER TEST BCHAPTER REVIEWSECTION QUIZ

SCILINKS ACTIVITY

MARINE ECOSYSTEMS

Go to www.scilinks.com. To find links relatedto marine ecosystems, type in the keywordHL5490. Then, use the links to answer thefollowing questions about marine ecosys-tems.

1. What percentage of the Earth’s surface iscovered by water?

2. What percentage of the Earth’s water is found in the oceans?

3. What is the largest animal on Earth?

4. Describe an ocean animal.

Name Class Date

SciLinks ActivityActivity

Developed and maintained by theNational Science Teachers Association

Topic: Reproductive SystemIrregularitiesSciLinks code: HL5490


Name Class Date

Vocabulary ActivityActivity

Getting the Dirt on the SoilAfter you finish reading Chapter: [Unique Title], try this puzzle! Use the clues belowto unscramble the vocabulary words. Write your answer in the space provided.

1. the breakdown of rock intosmaller and smaller pieces:AWERIGNETH

2. layer of rock lying beneath soil:CROKDEB

3. type of crop that is plantedbetween harvests to reduce soilerosion: CROVE

4. action of rocks and sedimentscraping against each other andwearing away exposed surfaces:SABRONIA

5. a mixture of small mineral frag-ments and organic matter: LISO

6. rock that is a source of soil:PRATEN CORK

7. type of reaction that occurs whenoxygen combines with iron toform rust: oxidation

8. type of weathering caused byphysical means: CLEMANIACH

9. the chemical breakdown of rocksand minerals into new substances: CAMILCHETHEARIGWEN

10. layers of soil, to a geologist:SNORHIZO

11. the uppermost layer of soil:SPOTOIL

12. process in which rainwater car-ries dissolved substances fromthe uppermost layers of soil to thebottom layers: HELANCIG

13. small particles of decayed plantand animal material in soil:MUUSH

14. the process in which wind, water,or ice moves soil from one location to another: ROOSINE

15. the methods humans use to takecare of soil:OSIL VASETONRICON

LONG-TERM PROJECTS & RESEARCH IDEAS

WHIZ-BANGDEMONSTRATIONS

WHIZ-BANGDEMONSTRATIONS

VOCABULARY AND SECTION SUMMARY


Section: EnergIn the space provided, write the letter of the description that best matches theterm or phrase.

______ 1. building molecules that can be used asan energy source. or breaking down moleculesin which energy is stored

______ 2. the process by which light energy is convertedto chemical energy

______ 3. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 4. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 5. an organism that consumes food to get energy

______ 6. the process of getting energy from food

In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.

Name Class Date

Section QuizAssessment

a. photosynthesis

b. autotroph

c. heterotroph

d. cellular respiration

e. metabolism

f. cellular respiration

______ 7. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd. logs burning in a fire

______ 8. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______ 9. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______10. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd.

logs burning in a fire


Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

4. What is one question you will answer as you explore physical science?

5. Chemistry and physics are both fields of . Chemists

study the different forms of and how they interact.

and how it affects are

studied in physics.

Identify the field of physical science to which each of the following descriptionsbelongs by writing physics or chemistry in the space provided.

_______________________ 6. how a compass works

_______________________ 7. why water boils at 100°C

_______________________ 8. how chlorine and sodium combine to form table salt

_______________________ 9. why you move to the right when the car you are inturns left

Directed Reading A

Name Class Date

Skills Worksheet

DIRECTED READING B

Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

Directed Reading B

Name Class Date

Skills Worksheet

Section: UniqueVOCABULARY

In your own words, write a definition of the following term in the space provided.

1. scientific method

2. technology

3. observation

Name Class Date

Vocabulary & NotesSkills Worksheet

Name Class Date

ReinforcementSkills Worksheet

The Plane TruthComplete this worksheet after you finish reading the Section: [Unique SectionTitle]

You plan to enter a paper airplane contest sponsoredby Talkin’ Physical Science magazine. The personwhose airplane flies the farthest wins a lifetime sub-scription to the magazine! The week before the con-test, you watch an airplane landing at a nearbyairport. You notice that the wings of the airplane haveflaps, as shown in the illustration at right. The paperairplanes you’ve been testing do not have wing flaps.What question would you ask yourself based on these observations? Write yourquestion in the space below for “State the problem.” Then tell how you could usethe other steps in the scientific method to investigate the problem.

1. State the problem.

2. Form a hypothesis.

3. Test the hypothesis.

4. Analyze the results.

5. Draw conclusions.

Flaps


CRITICAL THINKING

A Solar Solution

Name Class Date

Critical Thinking Skills Worksheet

Joseph D. Burns

Inventors’ Advisory Consultants

Portland, OR 97201

Dear Mr. Burns,I’ve got this great idea for a new product called the BlissHeater. It’s a portable, solar-powered space heater. The heater’s design includes these features:•T

he heater will be as longas an adult’s arm and aswide as a

packing box.

•T

he heater will have aglass top set at an angleto catch the sun’s rays.

•T

he inside of the heaterwill be dark colored toabsorb solar heat.If you think my idea will work, I will make the Bliss

Heaters right away without wasting time and money on test-ing and making models. Please write back soon with youropinion.

SECTION REVIEW

Section: UniqueKEY TERMS

1. What do paleontologist study?

2. How does a trace fossil differ from petrified wood?

3. Define fossil.

UNDERSTANDING KEY IDEAS

Name Class Date

Section ReviewSkills Worksheet


[UniqueMULTIPLE CHOICE


______ 1. Surface currents are formed by a. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.

______ 2. When waves come near the shore, a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.

______ 3. Longshore currents transport sediment a . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.

______ 4. Which of the following does NOT control surface currents?a. global wind c. Coriolis effectb. tides d. continental deflections

______ 5. Whitecaps break a. in the surf. c. in the open ocean.b. in the breaker zone. d. as their wavelength increases.

______ 6. Most ocean waves are formed by a . earthquakes. c. landsides.b. wind. d. impacts by cosmic bodies.

______ 7. Which factor controls surface currents? a. global winds c. continental deflectionb. the Coriolis effect d. all of the above

______ 8. Streamlike movments of ocean water far below the surface arecalleda. jet currents c. surface currents.b. Coriolis currents. d. deep currents.

______ 9. When the sunlit part of the moon that can be seen from Earthgrows larger, it is a. waxing. c. in the new moon phase.b. waning. d. in the full moon phase.

______10. The Milky Way is thought to be a. an elliptical galaxy. c. a spiral galaxy.

Name Class Date

Chapter Test BAssessment


READING

Read the passages below. Then, read each question that follows the passage.Decide which is the best answer to each question.

Passage 1 adventurous summer camp in the world. Billy can’twait to head for the outdoors. Billy checked the recommendedsupply list: light, summer clothes; sunscreen; rain gear; heavy,down-filled jacket; ski mask; and thick gloves. Wait a minute! Billythought he was traveling to only one destination, so why does heneed to bring such a wide variety of clothes? On further investiga-tion, Billy learns that the brochure advertises the opportunity to“climb the biomes of the world in just three days.” The destinationis Africa’s tallest mountain, Kilimanjaro.

______ 1. The word destination in this passage means A camp B vacation.C place. D mountain.

______ 2. Which of the following is a FACT in the passage? F People ski on Kilimanjaro.G Kilimanjaro is Africa’s tallest mountain.H It rains a lot on Kilimanjaro.J The summers are cold on Kilimanjaro.

______ 3. Billy wondered if the camp was advertising only one destination afterhe read the brochure, which said thatA the camp was the most adventurous summer camp in the world. B he would need light, summer clothes and sunscreen.C he would need light, summer clothes and a heavy, down-filled

jacket.D the summers are cold on Kilimanjaro.

Name Class Date

Standardized Test PreparationAssessment

PERFORMANCE-BASEDASSESSMENT

OBJECTIVEDetermine which factors cause some sugar shapes to break down faster than others.

KNOW THE SCORE!As you work through the activity, keep in mind that you will be earning a gradefor the following:

• how you form and test the hypothesis (30%)

• the quality of your analysis (40%)

• the clarity of your conclusions (30%)

ASK A QUESTIONSWhy do some sugar shapes erode more rapidly than others?

MATERIALS AND EQUIPMENT

Name Class Date

Performanced-Based AssessmentAssessment SKILL BUILDER

Using Scientific Methods

• 1 regular sugar cube • 90 mL of waterCopyright © by Holt, Rinehart and Winston. All rights reserved.

USING VOCABULARY

1. Define biome in your own words.

2. Describe the characteristics of a savanna and a desert.

3. Identify the relationship between tundra and permafrost.

4. Compare the open-water zone and the deep-water zone.

5. Use each of the following terms in an original sentence: plankton, littoralzone, and estuary.

6. Describe how marshes and swamps differ.

Name Class Date

Chapter ReviewSkills Worksheet

SCIENCE PUZZLERS, TWISTERS & TEASERS

CHAPTER TEST A






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test AAssessment

CHAPTER TEST C






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test CAssessment

For a preview of available worksheets covering math and science skills, see pages T26–T33. All of these resources are also on the One-Stop Planner®.

Chapter 11 • Chapter Resources 309D

As a Matter of Space

The never-ending quest to better understand our universe has led scientists to someamazing places, from the deep reaches of outer space to the heart of the atom. Our curiosity has shown us things smaller than anyone thought existed—first theatom and then subatomic particles. But scientists didn’t stop with protons, elec-trons, and neutrons. Instead, they devised sophisticated instruments called particleaccelerators to take a close look at subatomic particles. What they found were evensmaller subatomic particles, which they named quarks, positrons, and gluons. Willthey keep looking for something even smaller? Of course!

The Quirks of Quarks1. Find out more about subatomic particles like quarks. How

many different kinds of quarks are there? Where do quarksfit into the atomic model? Do they carry a charge? Whatis their mass? Write a scientific magazine article and builda model of the subatomic particle you researched.

Other Research Ideas2. How do you dig into a nucleus? Find out about particle

accelerators and cyclotrons in your library and on theInternet. How do they work? How many particle accelera-tors or cyclotrons exist in the United States? in the world?When was the first particle accelerator built? How big arethey? Write a newspaper article to report your findings.

3. How does a TV work? Television sets use cathode ray tubesto create a moving picture. How do cathode ray tubeswork? What other items besides television sets use cathoderay tubes? A new generation of television sets that are notmuch thicker than a picture frame are now on the market.Do they use cathode ray tubes or some other technology?Present your findings to the class in an oral presentationwith visual aids.

Long-Term Project Idea4. Arrange a tour of a commercial chemistry lab, environ-

mental chemistry lab, or the chemistry department at a university. What instruments are used in the lab to iden-tify atoms and compounds? What is the purpose of eachinstrument? Find out the primary fields of research beingexplored in that lab. If you have a camera, take pictures.Write an article describing your tour for the school paper.

Name ___________________________________________________ Date _________________ Class _____________

PROJECT

STUDENT WORKSHEET61

How Low Can They Go?

INTERNETKEYWORDS

cyclotron

particle accelerator

TEACHER-LED DEMONSTRATION

DEMO

54

Purpose

Students model the helium atom anddemonstrate that there is a vast amount ofempty space in the atom. This activity canbe used in conjunction with a discussionof the atomic models of Bohr andRutherford.

Time Required

15–20 minutes

What to Do

1. Find an area large enough to create acircle with a diameter of about 50 m.

2. Tell students that they will model thestructure of a helium atom. Choose avolunteer to hold the ball bearing andone end of both strings. Tell studentsthat the ball bearing represents the nu-cleus of an atom.

3. Tell students that the grains of sandrepresent electrons. Choose two morevolunteers to each hold an “electron.”

4. Ask the two students carrying a sandgrain to each pick up a different end ofstring and walk in opposite directions25 m from the “nucleus.”

5. Tell students that the distance betweenthe ball bearing and each sand grainrepresents the relative distance betweenthe nucleus of an atom and the firstring of electrons.

Explanation

In this activity, students have created theirown atomic model based on the models ofErnest Rutherford and Niels Bohr.

In 1911, Ernest Rutherford proposed anatomic model. He bombarded thin goldfoil with fast-moving, positively chargedparticles called alpha particles. To hisamazement, most of the particles passedthrough the foil without being deflected.After studying the results further,Rutherford and his colleagues concludedthat very few (one in 8,000) particles weredeflected back toward the source.Rutherford concluded that an atom’sstructure is mostly empty space surround-ing a dense, positively charged nucleus.He also concluded that the electrons orbitthe nucleus in the same way that planetsorbit the sun.

Rutherford continued studying theatom with Niels Bohr. In 1913, Bohr pro-posed his own model of the hydrogenatom. Bohr suggested that the electronsorbit in energy levels at discrete distancesfrom the nucleus.

As a Matter of Space

MATERIALS

• metric measuring tape• BB• 25 m lengths of string (2)• 2 grains of sand

Lee YassinskiSun Valley Middle School

Sun Valley, California

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

Going FurtherDiscuss the relative masses of protons andelectrons using one grain of rice to repre-sent an electron and 2,000 grains of rice(125 mL) to represent a proton.

PH

YSIC

AL S

CIE

NC

E

▼▼▼

TEACHER-LED DEMONSTRATION

DEMO

53

Candy LightsPurpose

Students see that crushing some materialscauses the materials to emit light, an effectknown as triboluminescence.

Time Required

15 minutes

Advance Preparation

This demonstration requires absolute dark-ness. If your classroom is difficult todarken completely, you may want to usean interior room, a large closet, or a darkstorage area. You may want to try thisdemonstration in advance to be certainthat conditions permit seeing the desiredeffect. Everyone should be wearing safetyglasses during the demonstration.

What to Do

1. Place the cutting board on a stable sur-face, such as a lab bench, desk, or floor.

2. Place 3–4 candies on the cutting board.

3. Ask students to gather around theboard so that they can all see the can-dies clearly.

4. Darken the room completely by turningoff all lights and sealing the windows.Wait a few minutes for everyone’s eyesto adjust to the darkness.

5. Ask students to watch the candiesclosely and observe what happens whenthe hammer hits them. Using the ham-mer, strike the candies several times.

6. Turn the lights back on. Encourage thestudents to discuss their observationsand offer explanations.

7. Discuss the various hypotheses as aclass.

Explanation

Students should see a flash of blue light asyou crush the candy. This effect is due tocharge separation between the pieces ofcandy and is called triboluminescence.

To help students understand what theyhave seen, you may wish to explain whathappened as follows: When the winter-green candy is crushed, the pieces of candytend to be left with extra electrical chargeson them. Some pieces are positivelycharged and therefore have fewer electronsthan protons, and some are negativelycharged and therefore have more electronsthan protons. The extra electrons on thenegatively charged pieces are free to move,so they flow to the positively chargedpieces. The excess charges cancel each otherout. This flow of charge is an electric cur-rent. As the electric current flows, it excitesthe atoms in its path, which then emit visi-ble light in response. This is the light ob-served in the activity.

This activity can be compared to the gen-eration of lightning in a thunderstorm.During a storm, excess charges tend to buildup in different parts of a cloud or clouds.Eventually, the excess negative charge flowsfrom one region to a region of excess posi-tive charge. The elec-tric current excitesair molecules thatemit the light we as-sociate with a light-ning bolt.

MATERIALS

• wooden or plastic cutting board• roll of wintergreen candies• hammer

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

Jerry TaylorSanta Maria Middle School

Phoenix, Arizona

Mystery Guests1. The three particles of an atom appeared recently on a talk show,

and they stood behind a screen to hide their identities. (Not thatyou could see them anyway.) Identify their statements below,based on what you know about their characteristics.a. I don’t mean to be negative all the time, but, well, I’m

always on the go.

b. Me? I stay positive. It’s the only way I know how to be.

c. I have almost no mass—no weight to throw around. And just once I’d like to be at the center of things.

d I stay neutral on most nuclear issues

Name _______________________________________________ Date ________________ Class______________

SCIENCE PUZZLERS, TWISTERS & TEASERS11

Introduction to Atoms

CHAPTER

Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.


Name Class Date

Reaction to StressQuick Lab DATASHEET FOR QUICK LAB

BackgroundThe graph below illustrates changes that occur in the membrane potential of aneuron during an action potential. Use the graph to answer the followingquestions. Refer to Figure 3 as needed.

Analysis1. Determine about how long an action potential lasts.

2. State whether voltage-gated sodium, chanels are open or closed at point A.

3. State whether voltage-gated potassium channels are open or closed atpoint B.

4. Critical Thinking Recognizing Relationships What causes the menberneotential to become less negative at point A?

5. Critical Thinking Recognizing Relationships What causes the membranepotential to become more negative at point B?


Answer here.

Answer here.

Answer here.

Answer here.

Answer here.

Using Scientific Methods

GENERAL

GENERALGENERAL

GENERAL

GENERAL

GENERAL

GENERAL

GENERAL

SPECIAL NEEDS

SPECIAL NEEDS GENERALGENERAL

GENERAL

SAMPLE

SAMPLE SAMPLE

SAMPLE SAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLESAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLE

DATASHEETS FORCHAPTER LABS

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

RATINGTeacher Prep–3Student Set-Up–2Concept Level–2Clean Up–2

MATERIALS

The materials listed on the student page are enough for a group of 4–5 students.Large, dried beans of any kind will work well in this exercise.

SAFETY CAUTION

Remind students to review all safety cautions and icons before beginning this labactivity.

Using Scientific MethodsSkills Practice Lab DATASHEET FOR CHAPTER LAB


1 2 3 4Easy Hard

Jason MarshMontevideo High

and Country School

SAMPLE

DATASHEETS FORLABBOOK

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

Does It All Add Up?Skills Practice Lab DATASHEET FOR LABBOOK LAB


Jason MarshM t id Hi h

SAMPLE

Chapter Enrichment

This Chapter Enrichment provides relevant and

interesting information to expand and enhance

your presentation of the chapter material.

Development of the Atomic TheoryDemocritus• Democritus (c. 460–c. 370 BCE) was a Greek philoso-

pher and leading advocate of the theory that all phe-nomena in nature could be understood in terms of the movements of particles called atoms (from the Greek word atomos, meaning “indivisible”).

• The views of Democritus sharply contrasted those of Aristotle and others, who held to the theory that all matter could be reduced to a combination of four elements: earth, water, air, and fire.

Is That a Fact!◆ Democritus’s ideas were not widely accepted because

Aristotle, who was better known and respected, did not accept the idea of atoms. Only fragments of Democritus’s writings survive, and most of our knowl-edge of his ideas comes from negative remarks about his theories in other people’s writings.

From Greek to Modern Atomic Theory• Democritus and other Greek philosophers laid the

groundwork for the modern atomic theory, but it was

not until the 16th and 17th centuries that interest in atoms and atomic structure was renewed. During that time, the work of Sir Isaac Newton, Robert Boyle, and Pierre Gassendi helped further the development of the atomic theory.

• In the 19th century, experiments by John Dalton, Amedeo Avogadro, James Clerk Maxwell, and Rudolf Clausius began to reveal the nature and structure of atoms.

• Sir Joseph John Thomson’s discovery of electrons in 1897 and his later research on protons and gases indicated that atoms were not the smallest indivisible units of matter, as previously thought. Thomson showed that subatomic particles with either a negative or positive charge form at least part of the structure of an atom. Thomson won the Nobel Prize in physics in 1906.

• While Thomson was director of the Cavendish Laboratory at Cambridge University in Cambridge, England, one of his graduate students was Ernest Rutherford. Rutherford went on to win the Nobel Prize in chemistry in 1908 for his work on radioactivity.

The AtomHow Small Are They?• Determining the diameter of an atom is difficult

because atoms are not small, hard spheres. Measurement often varies depending on the method used. On average, the diameter of an atom ranges from about 7 � 10–9 cm to 5 � 10–8 cm.

11

309E Chapter 11 • Introduction to Atoms

Quarks and Gluons• Protons and neutrons are composed of smaller parti-

cles called quarks. The existence of quarks was sug-gested in 1963 by two physicists: Murray Gell-Mann and George Zweig.

• Hadrons are all particles that feel the strong force. They include baryons, quark triplets; antibaryons; and mesons, quark-antiquark pairs. Baryons include pro-tons and neutrons.

• A gluon is believed to be a subatomic particle that “glues” quarks together with the strong nuclear force.

Is That a Fact!◆ When gluons bind to each other, they are referred

to as “glueballs.”

◆ The term quark originated from a line in James Joyce’s novel Finnegan’s Wake: “Three quarks for Muster Mark.”

Isotopes• While some isotopes are stable and can survive indefi-

nitely, others are unstable. Unstable isotopes undergo radioactive decay toward a more stable form, often by becoming other elements.

• There are approximately 280 stable isotopes of the natural elements. A natural element is usually predom-inantly one stable isotope with smaller amounts of other stable and unstable isotopes.

• Radioactive isotopes can be natural or artificial. The naturally occurring radioisotopes have existed since Earth’s formation.

• The first artificial radioisotopes were produced in 1934 by Frederic and Irene Joliot-Curie. Since then, more than 1,800 artificial radioisotopes have been produced by using a variety of nuclear bombardment techniques.

SciLinks is maintained by the National Science Teachers Association to provide you and your students with interesting, up-to-date links that will enrich your classroom presentation of the chapter.

Developed and maintained by theNational Science Teachers Association

Topic: Development of the Atomic Theory

SciLinks code: HSM0399

Topic: Current Atomic TheorySciLinks code: HSM0371

Topic: Inside the AtomSciLinks code: HSM0799

Topic: IsotopesSciLinks code: HSM0820

Visit www.scilinks.org and enter the SciLinks code for more information about the topic listed.

For background information about teaching strategies and

issues, refer to the Professional Reference for Teachers.

Chapter 11 • Chapter Enrichment 309F

Standards Correlations

National Science Education Standards

The following codes indicate the National Science EducationStandards that correlate to this chapter. The full text of thestandards is at the front of the book.

Chapter OpenerSAI 1, 2

Section 1 Development of the AtomicTheoryUCP 2; SAI 2; HNS 1, 2, 3

Section 2 The AtomPS 1c

Chapter LabSAI 2

Chapter ReviewHNS 2, 3

Science in ActionHNS 1

OverviewThis chapter discusses thedevelopment of the atomictheory over the years, from theprescientific ideas of Democritusthrough Dalton, Thomson, andRutherford to modern “electroncloud” theory. Then, the parts ofthe atom, including the forcesthat hold an atom together, aredescribed and discussed.

Assessing PriorKnowledgeStudents should be familiarwith the following topics:

• matter

• elements

IdentifyingMisconceptionsStudents often believe thatatoms possess macro propertiessuch as hardness, color, shape,or stickiness. They may alsobelieve that atoms contain noempty space and are static.

310 Chapter 11 • Introduction to Atoms

11

Introduction to Atoms

About the

You have probably made bubbles with aplastic wand and a soapy liquid. Somescientists make bubbles by using a bubblechamber. A bubble chamber is fi lled with apressurized liquid that forms bubbles when acharged particle moves through it. This photoshows the tracks made by charged particlesmoving through a bubble chamber. Bubblechambers help scientists learn about particlescalled atoms, which make up all objects.

Chain-of-EventsChart Before youread the chapter,

create the graphic organizer entitled“Chain-of-Events Chart” described in theStudy Skills section of the Appendix. Asyou read the chapter, fill in the chart withdetails about each step inthe historical developmentof ideas about atoms.

SECTION

Atoms are composedof small particles thatdetermine the propertiesof the atom.

11

1 Development of theAtomic Theory . . . . . . . . . . . . . 312

2 The Atom . . . . . . . . . . . . . . . . . 318

START-UPWhere Is It?Scientists have been able to gather information about atoms without actually seeing them. In this activity, you will do something similar: you will form an idea about the location and size of a hidden object by rolling marbles at it.

Procedure1. Place a rectangular piece of cardboard on four

books or blocks so that each corner of the card-board rests on a book or block.

2. Your teacher will place an unknown object under the cardboard. Be sure that you cannot see the object.

3. Place a large piece of paper on top of the cardboard.

4. Carefully roll a marble under the cardboard. Record on the paper the position where the marble enters and exits. Also, record the direction it travels.

5. Keep rolling the marble from different directions to collect data about the shape and location of the object. Write down all of your observations.

Analysis1. Form a conclusion about the object’s shape, size,

and location. Record your conclusion.

2. Lift the cardboard, and look at the object. Compare your conclusions with the object’s actual size, shape, and location.

Chapter 11 • Introduction to Atoms 311

START-UPSTART-UP vvM A T E R I A L S

FOR EACH GROUP• book or block (4)• cardboard, rectangular piece• marble• paper, plain, large piece• unknown object

Teacher’s Notes: The size of the cardboard should be large enough to prevent students from seeing the hidden object after you place it under the cardboard. Students will need to cover the cardboard completely with paper in order to mark the information they need to gather. Small pieces of wood cut into simple geometric shapes would work well as the objects used by each group.

Remind students to roll the marble gently as they try to establish where and what the object is.

Answer

1. Accept all reasonable answers. Students should make connec-tions between the behavior of the marble and the nature of the hidden object.

2. Accept all reasonable answers.

Would YouBelieve .

Introduction to Atoms CHAPTER STARTER

Tiny atoms have something in commonwith huge dinosaurs. In both cases, scientists have had to try to under-stand something they could not observefirsthand!

No one has ever seen a livingdinosaur, but scientists have determinedthe appearance of Tyrannosaurus rex bystudying fossilized skeletons. Scientiststheorize that these now-extinct creatureshad big hind legs, small front legs, a long, whip-like tail, and a mouth full ofdagger-shaped teeth.

However, theories of how T. rexwalked have been harder to develop. Formany years, most scientists thought thatT. rex plodded slowly like a big, lazylizard. However, after studying well-preserved dinosaur tracks, like thoseshown below, and noticing skeletal sim-ilarities between certain dinosaur fossilsand living creatures such as the ostrich,many scientists now theorize that T. rexcould turn on the speed. Some scientistsestimate that T. rex had bursts of speedof 32 km/h (20 mi/h)!

Theories about T. rex and otherdinosaurs have changed gradually basedon indirect evidence, such as dinosaurtracks. Likewise, our theory of the atomhas changed as scientists have uncoveredmore evidence about the atom, eventhough they were unable to see an atomdirectly. In this chapter, you’ll learn aboutthe development of the atomic theoryand our current understanding of atomicstructure.


Chapter Starter TransparencyUse this transparency to help students begin thinking about atoms.

CHAPTER RESOURCESTechnology

Transparencies• Chapter Starter Transparency

Student Edition on CD-ROM

Guided Reading Audio CD• English or Spanish

Classroom Videos• Brain Food Video Quiz

Workbooks

Science Puzzlers, Twisters & Teasers• Introduction to Atoms g

READINGSKILLS

READING STRATEGY

Development of the Atomic TheoryHave you ever watched a mystery movie and thought you knew who the criminal was? Have you ever changed your mind because of a new fact or clue?

The same thing happens in science! Sometimes an idea ormodel must be changed as new information is gathered. Inthis section, you will see how our ideas about atoms havechanged over time. Your first stop is ancient Greece.

The Beginning of Atomic TheoryImagine that you cut something in half. Then, you cut eachhalf in half again, and so on. Could you keep cutting thepieces in half forever? Around 440 BCE, a Greek philosophernamed Democritus (di MAHK ruh tuhs) thought that you wouldeventually end up with a particle that could not be cut. Hecalled this particle an atom. The word atom is from the Greekword atomos, meaning “not able to be divided.” Democritussaid that all atoms are small, hard particles. He thought thatatoms were made of a single material formed into differentshapes and sizes.

1

From Aristotle to Modern ScienceAristotle (AR is TAHT’l), another Greek philoso-pher, disagreed with Democritus’s ideas. Hebelieved that you would never end up with aparticle that could not be cut. He had such astrong influence on people’s ideas that for a longtime, most people thought he was right.

Democritus was right, though: Matter ismade of particles, which we call atoms. An atomatomis the smallest particle into which an elementcan be divided and still be the same substance.Figure 1 shows a picture of aluminum atomstaken with a scanning tunneling electron micro-scope (STM). Long before actually being able toscan atoms, scientists had ideas about them.

Figure 1 Aluminum cans, like all matter, are made of atoms. Aluminum atoms can be seen here as an image from a scanning tunneling electron microscope.

What You Will Learn

Describe some of the experimentsthat led to the current atomic theory.Compare the different models ofthe atom.Explain how the atomic theoryhas changed as scientists havedis covered new information aboutthe atom.

Vocabularyatom nucleuselectron electron cloud

Reading Organizer As you readthis section, create an outline of thesection. Use the headings from thesection in your outline.

OverviewStudents will trace changes thathave occurred in atomic theoryas scientists have discoveredmore about atomic structure.

BellringerDisplay the following quote byDemocritus (c. 460–c. 370 BCE).Have students write what theythink the statement means. Donot divulge the source.

Color exists by convention,sweet by convention, bitterby convention; in realitynothing exists but atoms andthe void.

Discuss Democritus and hisstatement with students.

vv---------------------------------------------------g

Photographic Dots Have stu-dents use a magnifying lens toexamine photographs in a news-paper. Students should noticethat the pictures are made upof tiny dots of ink. Explain thatmany objects that appear to bewhole are actually made up ofsmaller parts. It was this ideathat led early philosophers andscientists to theorize that matteris made up of tiny, indivisibleparts. These tiny bits of matterbecame known asatoms. l Visual ee

1

CHAPTER RESOURCES

Chapter Resource File

CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer

Workbooks

Interactive Textbook Struggling Readers Struggling Readers

Is That a Fact!It would take 1.05 � 1017 gold atoms tocover the entire surface of a dollar bill.That’s 105 quadrillion gold atoms!


Dalton’s Atomic Theory Based on ExperimentsBy the late 1700s, scientists had learned that elements combinein certain proportions based on mass to form compounds. Forexample, hydrogen and oxygen always combine in the sameproportion to form water. John Dalton, a British chemist andschoolteacher, wanted to know why. He experimented withdifferent substances. His results suggested that elements com-bine in certain proportions because they are made of singleatoms. Dalton, shown in Figure 2, published his atomic theoryin 1803. His theory stated the following ideas:

• All substances are made of atoms. Atoms are small particlesthat cannot be created, divided, or destroyed.

• Atoms of the same element are exactly alike, and atoms ofdifferent elements are different.

• Atoms join with other atoms to make new substances.

✓Reading Check Why did Dalton think that elements are madeof single atoms? (See the Appendix for answers to Reading Checks.)

Not Quite CorrectToward the end of the 1800s, scientists agreed that Dalton’stheory explained much of what they saw. However, newinformation was found that did not fit some of Dalton’s ideas.The atomic theory was then changed to describe the atom morecorrectly. As you read on, you will learn how Dalton’s theoryhas changed, step by step, into the modern atomic theory.

atom the smallest unit of anelement that maintains theproperties of that element

Figure 2 John Daltondeveloped his atomic theoryfrom observations gatheredfrom many experiments.

Answer to Reading Check

Dalton thought that elements are made of singleatoms because elements always combine inspecific proportions to form compounds.

Is That a Fact!Along with contributing to the atomictheory, John Dalton was also the first todescribe colorblindness. Dalton himselfwas colorblind. The paper that containshis article describing the condition waspublished in 1794.

GroupGroup vv ---------b

Scientist Flashcards Somestudents may benefit frommaking and using flashcards thatconnect the scientists profiled inthis section with their accom-plishments. Have students maketheir own sets of flashcards. Oneside of the card should featurethe name of the scientist, andthe other side should include asmall illustration representingthe model or experiment associ-ated with thescientist. l Visual ee

SUPPORT FOR

English LanguageLearnersEvolution of Atomic TheoryRemind students that ouridea of what the atom lookslike has changed throughouthistory. Explain that you aregoing to help them diagramwhat the atom looked like ac-cording to the theories in thissection to help them under-stand how we have come toour modern theory. After stu-dents read each theory, reviewit with them as a group anddraw the atom on the boardaccording to student descrip-tions of that theory. Label thediagrams with the name ofthe theory and leave them upfor student reference. Encour-age full participation. Whenall theories up to modern dayhave been diagrammed, askstudents to copy the progres-sion into their science jour-nals under each appropriatename.l Visual/Verbal

Section 1 • Development of the Atomic Theory 313

–

+

When the plates werecharged, the beam pro-duced a glowing spot hereafter being pulled towardthe positively charged plate.

Metal plates could becharged to change thepath of the beam.

When the plates were notcharged, the beam madea glowing spot here.

Almost all gas was removedfrom the glass tube.

An invisible beamwas produced whenthe tube was con-nected to a sourceof electrical energy.

Thomson’s Discovery of ElectronsIn 1897, a British scientist named J. J. Thomson showed thatthere was a mistake in Dalton’s theory. Thomson discoveredthat there are small particles inside the atom. This means thatatoms can be divided into even smaller parts.

Thomson experimented with a cathode-ray tube like theone shown in Figure 3. He discovered that a positively chargedplate (marked with a plus sign in the drawing) attracted thebeam. Thomson concluded that the beam was made of par-ticles that have negative electric charges. He also concludedthat these negatively charged particles are present in everykind of atom. The negatively charged particles that Thomsondiscovered are now called electrons.

Like Plums in a PuddingAfter learning that atoms contain electrons, Thomson pro-posed a new model of the atom. This model is shown inFigure 4. It is sometimes called the plum-pudding model, after adessert that was popular in Thomson’s day. Thomson thoughtthat electrons were mixed throughout an atom, like plums in apudding. Today, you might call Thomson’s model the chocolatechip ice-cream model.

Figure 4 Thomson proposedthat electrons were locatedthroughout an atom likeplums in a pudding, as shownin this model.

electron a subatomic particlethat has a negative charge

Thomson’s Cathode-Ray Tube ExperimentFigure 3

e

a

b

c

dCONNECTIONCONNECTION vvMath ----------------------------------------------------------------------------g

Counting Atoms The lengthof a dollar bill is 15.7 cm. Thewidth is 6.65 cm. If it takes 500million gold atoms laid end toend to measure the length ofa dollar bill, how many goldatoms would it take to measurethe width? (almost 212 million goldatoms) l Logical

h-----------------------------g

Writing Theories of AtomicStructure Thomson’smodel of the atom was

the first of many models createdto explain the atom’s structure.Each model is revised or replacedas scientists learn more. Currentmodels may be changed becauseof new discoveries. Have stu-dents write a paragraph explain-ing why making and usingmodels of scientific discoveriesis important. They should giveat least two reasons. l Logical

MISCONCEPTIONALERT

Charge Convention Theterms positive and negative arearbitrary. The terms were firstused by Benjamin Franklinto describe phenomena thathe observed. The terms werequickly adopted by scientists.


Transparencies• P45 Thomson’s Cathode-Ray Tube Experiment• P46 Rutherford’s Gold-Foil Experiment

Workbooks

Math Skills for Science• Using Proportions and Cross-

Multiplicationg

Is That a Fact!Thales of Miletus, the earliest knownGreek philosopher and scientist, is saidto have been the first person to observestatic electricity. He rubbed a piece ofamber with a wool cloth and observedthat lightweight objects were attractedto the amber.


Rutherford’s Atomic “Shooting Gallery”In 1909, a former student of Thomson’s named Ernest Rutherford decided to test Thomson’s theory. He designed an experiment to study the parts of the atom. He aimed a beam of small, positively charged particles at a thin sheet of gold foil. Figure 5 shows Rutherford’s experiment. Rutherford put a special coating behind the foil. The coating glowed when hit by the positively charged particles. Rutherford could then see where the particles went after hitting the gold.

✓Reading Check How could Rutherford tell where the positively charged particles went after hitting the gold foil?

Surprising ResultsRutherford started with Thomson’s idea that atoms are soft “blobs” of matter. He expected the particles to pass right through the gold in a straight line. Most of the particles did just that. But to Rutherford’s great surprise, some of the particles were deflected (turned to one side). Some even bounced straight back. Rutherford reportedly said,

Rutherford’s Gold-Foil ExperimentFigure 5

Solving Mysteries Scientists who made

discoveries about the atom had to do so by gathering clues and drawing conclusions from experiments. Read a short mystery story, and write a one-page paper in which you discuss the methods that were used to solve the mystery in the story. Compare these methods with those used by scientists finding out about what atoms are like.

WRITINGSKILL

A few particles bounced straight back.

e

Some particles were slightly deflected from a straight path.

d

An element such as radium produced the particles.

a

Lead stopped all of the positive particles except for a small stream aimed at a gold-foil target.

b

Most of the particles passed straight through the gold foil.

c


Discussion ----------------------------------gWriting Influences on Atomic

Theory Tell students to write in their science

journal a paragraph telling which person—Democritus, John Dalton, or J. J. Thomson—they believe had the greatest impact on present-day atomic theory. Then, encourage stu-dents to discuss and debate their choices. l Verbal/Logical

CONNECTIONCONNECTION vvLiterature ---------------------------------------------------g

The Shrinking Man In 1956, science-fiction author Richard Matheson published TheShrinking Man. In this story, which was later made into the film called The Incredible Shrinking Man, a man is con-taminated by a radioactive cloud and begins to shrink down to atomic size. Obtain a copy of Matheson’s story, and read excerpts to the students. The story suggests an eerie connec-tion between atomic space and the space of our solar system. l Auditory/Verbal


Rutherford could tell where the positively charged particles went because they hit a special coating that glowed where it was hit.

vv--------------------------------------aWriting Advanced Learners

Rutherford was influ-enced by the ideas of

Japanese physicist Hantaro Nagaoka, who in 1904 suggested that electrons circled in orbits within the atom. Have advanced learners research Japanese scien-tists such as Nagaoka, Hideki Yukawa, and Kenjiro Takayanagi and share with the class the con-tributions that these scientists made to modern science. l Logical

dates or time frames: 440 BCE, 384–322 BCE, late 1700s, 1897, 1909, and 1913.Ask each team to add its date, along with a name and an important idea, to the timeline. Have teams use magnets to mark their spots so that students with visual impairments can feel the spacing on the timeline. l Logical

StrategiesStrategiesINCLUSIONINCLUSION

• Visually Impaired • Developmentally Delayed• Hearing ImpairedSome students have difficulty under-standing the relationships between events in history. Divide the class into six teams. Draw on the board a long horizontal line that can be used as a timeline. Assign each team one of these

Where Are the Electrons?The plum-pudding model of the atom did not explain what Rutherford saw. Most of the tiny particles went straight through the gold foil, with a small number being deflected. He realized that in order to explain this, atoms must be considered mostly empty space, with a tiny part made of highly dense matter.

Far from the NucleusIn 1911, Rutherford revised the atomic theory. He made a new model of the atom, as shown in Figure 6. Rutherford proposed that in the center of the atom is a tiny, extremely dense, posi-tively charged part called the nucleus (NOO klee uhs). Because like charges repel, Rutherford reasoned that posi tively charged particles that passed close by the nucleus were pushed away by the positive charges in the nucleus. A particle that headed straight for a nucleus would be pushed almost straight back in the direction from which it came. From his results, Rutherford calculated that the diameter of the nu cleus was 100,000 times smaller than the diam eter of the gold atom. To get an idea of this kind of difference in size, look at Figure 7.

✓Reading Check How did Rutherford change Thomson’s model of the atom?

Bohr’s Electron LevelsIn 1913, Niels Bohr, a Danish scientist who worked with Rutherford, studied the way that atoms react to light. Bohr’s results led him to propose that electrons move around the nucleus in certain paths, or energy levels. In Bohr’s model, there are no paths between the levels. But electrons can jump from a path in one level to a path in another level. Think of the levels as rungs on a ladder. You can stand on the rungs of a ladder but not between the rungs. Bohr’s model was a valu-able tool in predicting some atomic behavior, but the atomic theory still had room for improvement.

nucleus in physical science, an atom’s central region, which is made up of protons and neutrons

electron cloud a region around the nucleus of an atom where elec-trons are likely to be found

Figure 7 The diameter of this pinhead is 100,000 times smaller than the diameter of the stadium. The pinhead represents the size of a nucleus, and the stadium represents the size of an atom.

Figure 6 Rutherford’s model of the atom had electrons surrounding the nucleus at a distance. (This model does not show the true scale of sizes and distances.)

Electron

Nucleus


Rutherford changed Thomson’s model of the atom by proposing that the nucleus is a tiny, dense, positively charged area surrounded by electrons.

Reteaching -------------------------------------bTable of Atomic DiscoveriesSummarize the scientists covered in this section and their discov-eries about the atom by con-structing a table on the board. The first column should consist of the name of each scientist, and the second column should briefly state what the scientist discovered. Ask students to ver-bally elaborate on how each dis-covery was made. l Visual

Quiz ---------------------------------------------------------------------g

1. What error did Thomson find in Dalton’s atomic theory? (Thomson discovered that atoms are made of smaller parts.)

2. What is the name for Thomson’s model of the atom? (the plum-pudding model)

3. What is the current model of the atom called? (the electron-cloud model)

Alternative Assessment ---------------------------g

Role-Playing Randomly call on students to get up in front of the class and role-play a cer-tain scientist or philosopher discussed in this section. Have them describe the experiment that was performed, what the individual was trying to find out, and what the individual discovered. l Verbal


For a variety of links related to thischapter, go to www.scilinks.org

SummarySummary

Review

The Modern Atomic TheoryMany 20th-century scientists added to our currentunderstanding of the atom. An Austrian physicist namedErwin Schrödinger (SHROH ding uhr) and a Germanphysicist named Werner Heisenberg (HIE zuhn berkh)did especially important work. They further explainedthe nature of electrons in the atom. For example,electrons do not travel in definite paths as Bohr sug-gested. In fact, the exact path of an electron cannotbe predicted. According to the current theory, there areregions inside the atom where electrons are likely tobe found. These regions are called electron clouds. Theelectron-cloud model of the atom is shown in Figure 8.

• Democritus thought thatmatter is composed ofatoms.

• Dalton based his theoryon observations of howelements combine.

• Thomson discoveredelectrons in atoms.

• Rutherford discoveredthat atoms are mostlyempty space with adense, positive nucleus.

• Bohr proposed thatelectrons are locatedin levels at certain dis-tances from the nucleus.

• The electron-cloudmodel represents thecurrent atomic theory.

Using Key Terms

1. In your own words, write adefinition for the term atom.

The statements below are false.For each statement, replace theunderlined term to make a truestatement.

2. A nucleus is a particle witha negative electric charge.

3. The electron is where mostof an atom’s mass is located.

Understanding Key Ideas

4. Which of the followingscientists discovered thatatoms contain electrons?

a. Daltonb. Thomsonc. Rutherfordd. Bohr

5. What did Dalton do indeveloping his theory thatDemocritus did not do?

6. What discovery demonstratedthat atoms are mostly emptyspace?

7. What refinements did Bohrmake to Rutherford’s proposedatomic theory?

Critical Thinking

8. Making Comparisons Com-pare the location of electronsin Bohr’s theory with the loca-tion of electrons in the currentatomic theory.

9. Analyzing Methods Howdoes the design of Rutherford’sexperiment show what he wastrying to find out?

Interpreting Graphics

10. What about the atomic modelshown below was shown to beincorrect?

Topic: Development of the Atomic Theory;Current Atomic Theory

SciLinks code: HSM0399; HSM0371

Electron cloudsNucleus

Figure 8 In the current model ofthe atom, electrons surround thenucleus in electron clouds.

Answers to Section Review

1. Sample answer: the small-est part of an element that hasthe properties of that element

2. electron3. nucleus4. b5. He performed experiments

and drew conclusions fromthem to develop his theory.

6. Rutherford’s gold-foil expe-riment, in which Rutherfordobserved that most of the posi-tively charged particles thathe aimed at a piece of goldfoil went straight through

7. Bohr suggested that elec-trons could move around thenucleus only in certain paths.They could jump from path topath, but not stay between thepaths.

8. Bohr’s theory held thatelectrons can travel only incertain paths around thenucleus. The current atomictheory is that electrons travelin regions where they are likelyto be found.

9. Rutherford placed a sur-face behind the gold foil, whichwould glow where the posi-tively charged particles hit it.This shows that he was tryingto find out where the particleswent after hitting the gold foil.

10. The model represents elec-trons as mixed throughout anatom. Rutherford showed thisarrangement to be incorrect.

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• Reinforcement Worksheetb

CRF


READING STRATEGY

2 The AtomEven though atoms are very small, they are made up of even smaller things. You can learn a lot about the parts that make up an atom and what holds an atom together.

In this section, you’ll learn about how atoms are alike andhow they are different. But first you’ll find out just how smallan atom really is.

How Small Is an Atom?Think about a penny. A penny contains about 2 � 1022 atoms(which can be written as 20,000,000,000,000,000,000,000atoms) of copper and zinc. That’s 20 thousand billion billionatoms—over 3,000,000,000,000 times more atoms than thereare people on Earth! If there are that many atoms in a penny,each atom must be very small.

Scientists know that aluminum is made of average-sized atoms. An aluminum atom has a diameter of about0.00000003 cm. That’s three one-hundred-millionths of acentimeter. Take a look at Figure 1. Even things that arevery thin, such as aluminum foil, are made up of very largenumbers of atoms.

Figure 1 This aluminum foil might seem thin to you. But it is about 50,000 atoms thick!

What You Will Learn

Describe the size of an atom.Name the parts of an atom.Describe the relationship betweennumbers of protons and neutronsand atomic number.State how isotopes differ.Calculate atomic masses.Describe the forces within an atom.

Vocabularyproton atomic numberatomic mass isotope unit mass numberneutron atomic mass

Reading Organizer As you readthis section, make a concept map byusing the terms above.

OverviewThis section describes what isknown about the particles insidean atom. Students will learnabout the atomic number andmass number of an atom andabout charge and isotopes.Finally, students will calculatethe atomic mass of an elementand determine the number ofparticles within an atom.

BellringerTell students that an atom is thesmallest particle into which anelement can be divided and stillbe that element. Now that scien-tists have learned that an atomis made up of even smaller parti-cles, is this definition still accu-rate? Explain your answer.

Discussion ----------------------------------gThe Atomic Scale Studentsmay have difficulty visualizingthe very large and very smallnumbers that are used whenatoms are discussed. Give eachstudent a penny to hold andlook at while the class discussesthe large number of atoms inthe penny and the extremelysmall size of each atom. l Visual

2

Is That a Fact!One molecule of water is composed ofthree atoms—two hydrogen atoms andone oxygen atom. One molecule ofnatural rubber is composed of approxi-mately 295,000 atoms—175,000 carbonatoms and 120,000 hydrogen atoms.

CHAPTER RESOURCES


CRF • Lesson Plan• Directed Reading Ab• Directed Reading Bs

Technology

Transparencies• Bellringer• P47 Parts of an Atom

Workbooks

Interactive Textbook Struggling Readers Struggling Readers


What Is an Atom Made Of?As tiny as an atom is, it is made up of even smaller particles. These particles are protons, neutrons, and electrons, shown in the model in Figure 2. (The particles in the pictures are not shown in their correct proportions. If they were, the electrons would be too small to see.)

The NucleusProtons are positively charged particles in the nucleus. The mass of a proton is about 1.7 � 10–24 g. This number can also be written as 0.0000000000000000000000017 g. Because the masses of particles in atoms are so small, scientists made a new unit for them. The SI unit used to express the masses of particles in atoms is the atomic mass unit (amu). Each proton has a mass of about 1 amu.

Neutrons are the particles of the nucleus that have no electrical charge. Neutrons are a little more massive than protons are. But the difference in mass is so small that the mass of a neutron can be thought of as 1 amu.

Protons and neutrons are the most massive particles in an atom. But the volume of the nucleus is very small. So, the nucleus is very dense. If it were possible to have a nucleus the volume of a grape, that nucleus would have a mass greater than 9 million metric tons!

✓Reading Check Name the two kinds of particles that can be found in the nucleus. (See the Appendix for answers to Reading Checks.)

proton a subatomic particle that has a positive charge and that is found in the nucleus of an atom

atomic mass unit a unit of mass that describes the mass of an atom or molecule

neutron a subatomic particle that has no charge and that is found in the nucleus of an atom

Protons are positively charged par-ticles in the nucleus of an atom.

Neutrons are particles in the nucleus of an atom that have no charge.

Electrons are negatively charged particles found in electron clouds outside the nucleus. The size of the electron clouds determines the size of the atom.

The nucleus is the small, dense, positively charged center of the atom. It contains most of the atom’s mass.

The diameter of the nucleus is 1/100,000 the diameter of the atom.

Parts of an AtomFigure 2

Section 2 • The Atom 319

READINGSTRATEGY ------------------g

Atomic Diagrams As students learn about the particles inside an atom, have them create and label diagrams of several different atoms in their science journal.Students can use Figures 2–5 as guidelines. The diagrams should show the different parti-cles, their locations, and other information, such as mass and charge. l Visual/Logical ee

MISCONCEPTIONALERT

Atomic Size When students think of the smallest particle possible, they may picture a dust particle. As they read through this section, help them understand how small an atom is. Even one dust particle is made of millions of atoms!

CONNECTIONCONNECTION vvReal World ---------------------------------------------g

Powers of 10 Attempting to comprehend the size and the components of atoms interests people other than chemists and physicists. Charles and Ray Eames were architects and designers who were fascinated with size and numbers. This interest led them to make the award-winning film Powers of Ten (1977). The film is available on video and is a fascinating exploration into the “small” of atoms and the “large” of the universe. l Visual


Protons and neutrons can be found in the nucleus.

Is That a Fact!Carbon-12 is used by scientists to deter-mine an atomic mass unit (amu). The amu is exactly one-twelfth the mass of a carbon-12 atom. Because carbon-12 has six protons and six neutrons in its nucleus, the mass of a proton and the mass of a neutron are each considered to be 1 amu.

A neutron walks into a diner and orders a glass of orange juice at the lunch counter. When the waiter brings the juice, the neutron asks, “How much do I owe you?”

The waiter replies, “For you, no charge.”

Outside the NucleusElectrons are the negatively charged particles in atoms.Electrons are found around the nucleus within electron clouds.Compared with protons and neutrons, electrons are very smallin mass. It takes more than 1,800 electrons to equal the massof 1 proton. The mass of an electron is so small that it isusually thought of as almost zero.

The charges of protons and electrons are opposite butequal, so their charges cancel out. Because an atom has nooverall charge, it is neutral. What happens if the numbers ofelectrons and protons are not equal? The atom becomes a chargedparticle called an ion (IE ahn). An atom that loses one or moreelectrons becomes a positively-charged ion. An atom that gainsone or more electrons becomes a negatively-charged ion.

✓Reading Check How does an atom become a positively-

charged ion?

How Do Atoms of Different Elements Differ?There are more than 110 different elements. The atoms of eachof these elements are different from the atoms of all otherelements. What makes atoms different from each other? Tofind out, imagine that you could build an atom by puttingtogether protons, neutrons, and electrons.

Proton

ElectronNeutron

Figure 3 A helium nucleus musthave neutrons in it to keep theprotons from moving apart.

Starting SimplyIt’s easiest to start with the simplest atom.Protons and electrons are found in all atoms.The simplest atom is made of just one of each.It’s so simple it doesn’t even have a neutron. To“build” this atom, put just one proton in thecenter of the atom for the nucleus. Then, putone electron in the electron cloud. Congratula-tions! You have just made a hydrogen atom.

Now for Some NeutronsNow, build an atom that has two protons. Bothof the protons are positively charged, so theyrepel one another. You cannot form a nucleuswith them unless you add some neutrons. Forthis atom, two neutrons will do. To have aneutral charge, your new atom will also needtwo electrons outside the nucleus. What youhave is an atom of the element helium. Amodel of this atom is shown in Figure 3.

Hydrogen Hydrogen is themost abundant element inthe universe. It is the fuel forthe sun and other stars. It iscurrently believed that thereare roughly 2,000 times morehydrogen atoms than oxygenatoms and 10,000 times morehydrogen atoms than carbonatoms.

Make a model of a hydrogenatom using materials of yourchoice to represent a hydrogenatom’s proton and electron.Present the model to the class,and explain in what waysyour model resembles ahydrogen atom.

Quarks Scientists havelearned that protons andneutrons are composed ofeven smaller particles calledquarks. There are six kindsof quarks, which scientistshave labeled “up,” “down,”“charm,” “strange,” “top,”and “bottom.” The labels areused to tell one type of quarkfrom another; they don’treally describe the quarks.


An atom becomes a positivelycharged ion when it loses anelectron.

CONNECTION toCONNECTION toEarth Science ----------------------g

Fusion of Hydrogen in the SunIn the sun (as well as other stars),hydrogen nuclei are fused in anuclear reaction to form helium.This nuclear reaction gives off atremendous amount of energy,which is given off in the form ofelectromagnetic radiation and isresponsible for the light we seeand heat we feel from the sun.Use the teaching transparency“Fusion of Hydrogen in the Sun.”


Transparencies• P48 Forces in the Atom• LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E87 Fusion of Hydrogen

in the Sun


Building Bigger AtomsYou could build a carbon atom using 6 protons, 6 neutrons,and 6 electrons. You could build an oxygen atom using 8protons, 9 neutrons, and 8 electrons. You could even build agold atom with 79 protons, 118 neutrons, and 79 electrons!As you can see, an atom does not have to have equal numbersof protons and neutrons.

Protons and Atomic NumberHow can you tell which elements these atoms represent? Thekey is the number of protons. The number of protons in thenucleus of an atom is the atomic number of that atom. All atomsof an element have the same atomic number. Every hydrogenatom has only one proton in its nucleus, so hydrogen has anatomic number of 1. Every carbon atom has six protons in itsnucleus. So, carbon has an atomic number of 6.

IsotopesAn atom that has one proton, one electron, and one neutronis shown in Figure 4. The atomic number of this new atomis 1, so the atom is hydrogen. However, this hydrogen atom’snucleus has two particles. Therefore, this atom has a greatermass than the hydrogen atom you made.

The new atom is another isotope (IE suh TOHP) of hydrogen.Isotopes are atoms that have the same number of protons buthave different numbers of neutrons. Atoms that are isotopesof each other are always the same element, because isotopesalways have the same number of protons. They have differentnumbers of neutrons, however, which gives them differentmasses.

atomic number the number ofprotons in the nucleus of an atom;the atomic number is the same forall atoms of an element

isotope an atom that has the samenumber of protons (or the sameatomic number) as other atoms ofthe same element do but that has adifferent number of neutrons (andthus a different atomic mass)

Neutron

ElectronProtonElectronProton

Isotopes of HydrogenFigure 4

This isotope is a hydrogenatom that has one proton andone neutron in its nucleus.

This isotope is a hydrogenatom that has one protonin its nucleus.

For another activity relatedto this chapter, go togo.hrw.com and type in thekeyword HP5ATSW.

StrategiesStrategiesINCLUSIONINCLUSION

• Attention Deficit Disorder• Developmentally Delayed• Learning DisabledOrganize students into teamsof six. Within each team, asktwo students to wear “pro-ton” signs, two to wear “elec-tron” signs, and two to wear“neutron” signs. Give eachteam a hula hoop to placeon the floor to represent theboundary of the nucleus.Ask teams to form each ofthe following:

1. a simple hydrogen atom

2. an isotope of hydrogen

3. an isotope of hydrogenthat is different from theone formed by the teamon the left

4. an atom that is not hydro-gen (because each teamhas only two protons,each team will formsimple helium atomsor isotopes of them)

l Kinesthetic/Interpersonal

CONNECTION toCONNECTION toPaleontology --------------------------------g

Carbon Dating The isotope carbon-14 isused in radiocarbon dating of animal andplant fossils. Uranium-238, uranium-235,and thorium-232 are isotopes that scien-tists use to tell the age of rocks andmeteorites.

Have you heard the one about thechemist who was reading a book abouthelium? He couldn’t put it down.

SUPPORT FOR

English LanguageLearnersAtomic Numbers and theElements Students may havehad limited exposure to theperiodic table in their firstcountries. When studentshave finished reading thepage, display a large versionof the periodic table and dis-tribute a copy of the periodictable to each student. Explainthat this table shows all ofthe known elements. Elicitfrom students the definitionof atomic number, and helpthem find the atomic num-ber of different elements byusing the periodic table. (Theatomic number is the numberabove the chemical symbol.)Model correct pronunciationof the elements as needed.l Visual/Logical


Properties of IsotopesEach element has a limited number of isotopes that arefound in nature. Some isotopes of an element have specialproperties because they are unstable. An unstable atom is anatom with a nucleus that will change over time. This typeof isotope is radioactive. Radioactive atoms spontaneously fallapart after a certain amount of time. As they do, they give offsmaller particles, as well as energy.

However, isotopes of an element share most of the samechemical and physical properties. For example, the mostcommon oxygen isotope has 8 neutrons in the nucleus. Otherisotopes of oxygen have 9 or 10 neutrons. All three isotopesare colorless, odorless gases at room temperature. Each isotopehas the chemical property of combining with a substance as itburns. Different isotopes of an element even behave the samein chemical changes in your body.

✓✓Reading Check In what cases are differences between isotopes important?

Telling Isotopes ApartYou can identify each isotope of an element by its massnumber. The mass numbermass number is the sum of the protons andneutrons in an atom. Electrons are not included in an atom’smass number because their mass is so small that they havevery little effect on the atom’s total mass. Look at the boronisotope models shown in Figure 5 to see how to calculate anatom’s mass number.

mass numbermass number the sum of the numbers of protons and neutrons in the nucleus of an atom

Each of these boron isotopes has five protons. But because each has a different number of neutrons, each has a different mass number.

Protons: 5Neutrons: 5Electrons: 5Mass number � protons � neutrons � 10

Protons: 5Neutrons: 6Electrons: 5Mass number � protons � neutrons � 11

Atomic DiagramsExplain what you have learned about isotopes to an adult. Together, draw diagrams of hydrogen-2, helium-3, and carbon-14. Show the correct number and location of each type of particle. For the electrons, simply write the total number of electrons in the electron cloud. Use colored pencils or markers to represent the pro-tons, neutrons, and electrons.

Isotopes of BoronFigure 5

CONNECTIONCONNECTION vvLife Science ------------------------------------g

Uses of Isotopes Isotopes havemany applications in the field ofnuclear medicine. Cobalt-60 isused to treat cancerous tumors,and iodine-131 is used in thetreatment of hyperthyroidism.Have students research the useof radioactive isotopes in thedetection and treatment of dis-ease. Students can present theirresults in posters, concept maps,or reports. l Logical


Differences between isotopes areimportant when a certain isotope isradioactive.

vv--------------------------------------g

M A T E R I A L SFOR EACH STUDENT• colored dots (available at

office-supply stores)• construction paper• markers

Reconstructing Atoms

1. Distribute dots, paper, andmarkers to students.

2. Have students study theatoms shown in Figures 2–5.

3. Instruct students to recon-struct each of the isotopes.Students should use adifferent-colored dot forthe protons, neutrons, andelectrons.

4. Remind students to noticethat only the number of neu-trons changes from isotopeto isotope.

l Visual

Is That a Fact!There are at least 2,670 known isotopes.Tin has 38 isotopes, the most of any ofthe elements. The least stable isotope islithium-5, which decays in 4.4 � 10–22 s.


12 Mass number� 6 Number of protons (atomic number) 6 Number of neutrons

Naming IsotopesTo identify a specific isotope of an element, write the name of the element followed by a hyphen and the mass number of the isotope. A hydrogen atom with one proton and no neutrons has a mass number of 1. Its name is hydrogen-1. Hydrogen-2 has one proton and one neutron. The carbon isotope with a mass number of 12 is called carbon-12. If you know that the atomic number for carbon is 6, you can calculate the number of neutrons in carbon-12 by subtracting the atomic number from the mass number. For carbon-12, the number of neutrons is 12 � 6, or 6.

Calculating the Mass of an ElementMost elements contain a mixture of two or more isotopes. For example, all copper is composed of copper-63 atoms and copper-65 atoms. The atomic mass of an element is the weighted average of the masses of all the naturally occurring isotopes of that element. A weighted average accounts for the percentages of each isotope that are present. Copper, including the copper in the Statue of Liberty, shown in Figure 6, is 69% copper-63 and 31% copper-65. The atomic mass of copper is 63.6 amu.

Figure 6 The copper used to make the Statue of Liberty includes both copper-63 and copper-65. Copper’s atomic mass is 63.6 amu.

atomic mass the mass of an atom expressed in atomic mass units

Atomic Mass Chlorine-35 makes up 76% of all the chlorine in nature, and chlorine-37 makes up the other 24%. What is the atomic mass of chlorine?

Step 1: Multiply the mass number of each isotope by its percentage abundance in decimal form.

Step 2: Add these amounts together to find the atomic mass.

Now It’s Your Turn1. Calculate the atomic mass of boron,

which occurs naturally as 20% boron-10 and 80% boron-11.

2. Calculate the atomic mass of rubidium, which occurs naturally as 72% rubidium-85 and 28% rubidium-87.

3. Calculate the atomic mass of gallium, which occurs naturally as 60% gallium-69 and 40% gallium-71.

4. Calculate the atomic mass of silver, which occurs naturally as 52% silver-107 and 48% silver-109.

5. Calculate the atomic mass of silicon, which occurs naturally as 92% silicon-28, 5% silicon-29, and 3% silicon-30.

(35 � 0.76) � 26.60(37 � 0.24) � � 8.88

35.48 amu

(35 � 0.76) � 26.60(37 � 0.24) � 8.88


CONNECTIONCONNECTION vvMath ----------------------------------------------------------------------------g

Calculating Atomic Mass Show students an example of how to calculate atomic mass. Use the information given for copper-63 and copper-65 on this page. Let students fill in some missing numbers. Label each of the values.

(63 � 0.69) � 43.47 amu(65 � 0.31) � 20.15 amu

43.47 � 20.15 � 63.62 amuNow, have students calculate the atomic mass of titanium. The five isotopes of titanium appear below.

titanium-46 (8.0%)

titanium-47 (7.3%)

titanium-48 (73.8%)

titanium-49 (5.5%)

titanium-50 (5.4%)

(47.9 amu)l Logical

Answers to Math Focus

1. (0.20 � 10 amu) � (0.80 �11 amu) � 10.8 amu

2. (0.72 � 85 amu) � (0.28 �87 amu) � 85.56 amu

3. (0.60 � 69 amu) � (0.40 �71 amu) � 69.8 amu

4. (0.52 � 107 amu) � (0.48 �109 amu) � 107.96 amu

5. (0.92 � 28 amu) � (0.05 �29 amu) � (0.03 � 30 amu) �28.11 amu

CHAPTER RESOURCESWorkbooks

Math Skills for Science • Arithmetic with Decimals g

MISCONCEPTIONALERT

Atomic Masses The atomic mass of copper shown on this page differs from that shown on the periodic table. The atomic mass of an element is calculated from the relative atomic masses of each isotope, not from the mass numbers. Relative atomic masses account for the fact that protons and neutrons are not exactly 1 amu and that electrons do have some mass.

Forces in AtomsYou have seen that atoms are made of smaller particles. But what are the forces (the pushes or pulls between objects) acting between these particles? Four basic forces are at work every-where, even within the atom. These forces are gravitational force, electromagnetic force, strong force, and weak force. These forces work together to give an atom its structure and proper-ties. Look at Figure 7 to learn about each one.

✓Reading Check What are the four basic forces at work everywhere in nature?

Weak Force The weak force is an important force in radioac-tive atoms. In certain unstable atoms, a neutron can change into a proton and an electron. The weak force plays a key role in this change.

Strong Force Protons push away from one another because of the electromagnetic force. A nucleus containing two or more protons would fly apart if it were not for the strongforce. At the close distances between protons and neutrons in the nucleus, the strong force is greater than the electromag-netic force, so the nucleus stays together.

Electromagnetic Force As men-tioned earlier, objects that have the same charge repel each other, while objects with opposite charge attract each other. This is due to the electromagneticforce. Protons and electrons are attracted to each other because they have opposite charges. The electromagnetic force holds the electrons around the nucleus.

Gravitational Force Probably the most familiar of the four forces is gravitational force. Gravitational force acts between all objects all the time. The amount of gravitational force between objects depends on their masses and the distance between them. Gravitational force pulls objects, such as the sun, Earth, cars, and books, toward one another. However, because the masses of particles in atoms are so small, the gravitational force within atoms is very small.

Particles with the same charges repel each other.

Forces in the AtomFigure 7

Particles with opposite charges attract each other.



The four basic forces are the gravitational force, electromagnetic force, strong force, and weak force.

Reteaching -------------------------------------bDescriptions of Atomic Structure Have students write a simple description of an atom for somebody who knows noth-ing about atoms. For example, students might explain atoms and atomic structure to a young child. Encourage students to use diagrams and examples in their descriptions. l Verbal

Quiz ---------------------------------------------------------------------g

1. What is an atom’s mass num-ber equal to? (the total number of protons and neutrons in that atom)

2. How is the atomic mass of an element calculated? (by taking a weighted average of the mass numbers of the isotopes of that element)

3. How do isotopes differ from one another? (in the number of neutrons that they have)

Alternative Assessment ---------------------------g

Concept Mapping Have stu-dents use the following terms to create a concept map: proton, atomic mass unit, neutron, atomic number, isotopes, mass number, and atomic mass.l Visual

For a variety of links related to thischapter, go to www.scilinks.org

SummarySummary

Review

Topic: Inside the Atom; IsotopesSciLinks code: HSM0799; HSM0820

Using Key Terms

1. Use the following terms in the same sentence:proton, neutron, and isotope.

Complete each of the following sentences bychoosing the correct term from the word bank.

atomic mass unit atomic numbermass number atomic mass

2. An atom’s is equal to the number ofprotons in its nucleus.

3. An atom’s is equal to the weightedaverage of the masses of all the naturallyoccurring isotopes of that element.

Understanding Key Ideas

4. Which of the following particles has noelectric charge?

a. protonb. neutronc. electrond. ion

5. Name and describe the four forces that are atwork within the nucleus of an atom.

Math Skills

6. The metal thallium occurs naturally as 30%thallium-203 and 70% thallium-205. Calculatethe atomic mass of thallium.

Critical Thinking

7. Analyzing Ideas Why is gravitational force inthe nucleus so small?

8. Predicting Consequences Could a nucleus ofmore than one proton but no neutrons exist?Explain.

Interpreting Graphics

9. Look at the two atomic models below. Do thetwo atoms represent different elements ordifferent isotopes? Explain.

NeutronProton

Electron NeutronProton

Electron

• Atoms are extremely small. Ordinary-sizedobjects are made up of very large numbersof atoms.

• Atoms consist of a nucleus, whichhas protons and usually neutrons, andelectrons, located in electron cloudsaround the nucleus.

• The number of protons in the nucleus ofan atom is that atom’s atomic number.All atoms of an element have the sameatomic number.

• Different isotopes of an element havedifferent numbers of neutrons in theirnuclei. Isotopes of an element sharemost chemical and physical properties.

• The mass number of an atom is the sumof the atom’s neutrons and protons.

• Atomic mass is a weighted average of themasses of natural isotopes of an element.

• The forces at work in an atom aregravitational force, electromagnetic force,strong force, and weak force.

Answers to Section Review

1. Sample answer: Different iso-topes have the same number ofprotons but different numbers ofneutrons.

2. atomic number3. atomic mass4. b5. Gravitational force acts between

objects based on their mass.Electromagnetic force attractsobjects of opposite electriccharge and repels objects of thesame electric charge. The strongforce holds the protons and neu-trons of atomic nuclei together.The weak force plays a role inradioactive decay.

6. (0.30 � 203 amu) � (0.70 �205 amu) � 204.4 amu

7. Gravitational force in the nucleusis so small because the massesof nuclear particles are so small.

8. no; Without neutrons, two pro-tons brought into close contactwould repel each other.

9. The two atoms shown are dif-ferent elements—they have different numbers of protons.

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• Critical Thinkinga• SciLinks Activityg

CRF


Model-Making Lab

Build models of nuclei ofcertain isotopes.

Use the periodic table todetermine the composition ofatomic nuclei.

• periodic table

• plastic-foam balls, blue,2–3 cm in diameter (6)

• plastic-foam balls, white,2–3 cm in diameter (4)

• toothpicks (20)

Made to OrderImagine that you are an employee at the Elements-4-UCompany, which custom builds elements. Your job is toconstruct the atomic nucleus for each element ordered byyour clients. You were hired for the position because of yourknowledge about what a nucleus is made of and yourunderstanding of how isotopes of an element differ from eachother. Now, it’s time to put that knowledge to work!

Procedure

1 Copy the table below onto another sheet of paper. Be sure toleave room to expand the table to include more elements.

2 Your first assignment is the nucleus of hydrogen-1. Pick up oneproton (a white plastic-foam ball). Congratulations! You havebuilt a hydrogen-1 nucleus, the simplest nucleus possible.

3 Count the number of protons and neutrons in the nucleus,and fill in rows 1 and 2 for this element in the table.

4 Use the information in rows 1 and 2 to determine the atomicnumber and mass number of the element. Record thisinformation in the table.

Data Collection Table

Hydrogen-1 Hydrogen-2 Helium-3 Helium-4 Beryllium-9 Beryllium-10

Numberof protons

Numberof neutrons

Atomicnumber

Massnumber

OBJECTIVES

SAFETY

MATERIALS

DO NOT WRITE IN BOOK

OT WRITE IN BOOK

Model-MakingModel-Making LabLab

Made to Order

Teacher’s NotesTeacher’s Notes

Time RequiredOne 45-minute class period

Lab Ratings

rTeacher Prep ff

Student Set-Up f

Concept Level fff

Clean Up f

M A T E R I A L SThe supplies listed are for a pair ofstudents. Foam balls of any color areacceptable as long as there are twocolors. Flexible pipe cleaners maybe used instead of toothpicks.

Safety CautionRemind students to review allsafety cautions and icons beforebeginning this lab activity.

Preparation NotesBefore you begin this lab, reviewthe concepts of isotopes, atomicnumber, and mass number.

To create colored balls, usecolored markers or spray paint.Alternatively, you can labelwhite balls “N” or “P.”

CHAPTER RESOURCES


CRF • Datasheet for Chapter Lab• Lab Notes and Answers

Technology

Classroom Videos• Lab Video

Sharon L. Woolf

Langston HughesMiddle SchoolReston, Virginia

Holt Lab Generator CD-ROMSearch for any lab by topic, standard, difficulty level,or time. Edit any lab to fit your needs, or create yourown labs. Use the Lab Materials QuickList softwareto customize your lab materials list.

CLASSROOM

TESTED& APPRO

VED


Carbon

6C

5 Draw a picture of your model.

6 Hydrogen-2 is an isotope of hydrogen that has one proton and one neutron. Using a strong-force connector, add a neutron to your hydrogen-1 nucleus. (Remember that in a nucleus, the protons and neutrons are held together by the strong force, which is represented in this activity by the toothpicks.) Repeat steps 3–5.

7 Helium-3 is an isotope of helium that has two protons and one neutron. Add one pro-ton to your hydrogen-2 nucleus to create a helium-3 nucleus. Each particle should be con-nected to the other two particles so that they make a triangle, not a line. Protons and neu-trons always form the smallest arrangement possible because the strong force pulls them together. Then, repeat steps 3–5.

8 For the next part of the lab, you will need to use information from the periodic table of the elements. Look at the illustration below. It shows the periodic table entry for carbon. You can find the atomic number of any element at the top of its entry on the periodic table. For example, the atomic number of carbon is 6.

9 Use the information in the periodic table to build models of the following isotopes of elements: helium-4, lithium-7, beryllium-9, and beryllium-10. Remember to put the protons and neutrons as close together as possible—each particle should attach to at least two others. Repeat steps 3–5 for each isotope.

Analyze the Results

1 Examining Data What is the relationship between the number of protons and the atomic number?

2 Analyzing Data If you know the atomic number and the mass number of an isotope, how could you figure out the number of neutrons in its nucleus?

Draw Conclusions

3 Applying Conclusions Look up uranium on the periodic table. What is the atomic number of uranium? How many neutrons does the isotope uranium-235 have?

4 Evaluating Models Compare your model with the models of your classmates. How are the models similar? How are they different?

Applying Your DataCombine your model with one that another student has made to create a single nucleus. Identify the element (and isotope) you have created.

Atomicnumber

Chapter 11 • Chapter Lab 327

Analyze the Results

1. The number of protons is the same as the atomic number.

2. The number of neutrons equals the mass number minus the atomic number.

Draw Conclusions

3. 92; 143 neutrons (235 – 92 = 143)

4. Sample answer: They differ in the way the protons and neutrons are connected to each other. They are the same in the number of protons and neutrons that each of the same isotope has, however.

Applying Your DataIf all of the protons and neutrons are used, the isotope created will be oxygen-20.

CHAPTER RESOURCESWorkbooks

Whiz-Bang Demonstrations• As a Matter of Space b• Candy Lights g

Long-Term Projects & Research Ideas• How Low Can They Go? a

The statements below are false. For each statement, replace the underlined term to make a true statement.

1 Electrons have a positive charge.

2 All atoms of the same element contain the same number of neutrons.

3 Protons have no electrical charge.

4 The atomic number of an element is the number of protons and neutrons in the nucleus.

5 The mass number is an average of the masses of all naturally occurring isotopes of an element.

Multiple Choice

6 The discovery of which particle proved that the atom is not indivisible?

a. protonb. neutronc. electrond. nucleus

7 How many protons does an atom with an atomic number of 23 and a mass number of 51 have?

a. 23b. 28c. 51d. 74

8 In Rutherford’s gold-foil experiment, Rutherford concluded that the atom is mostly empty space with a small, mas-sive, positively charged center because

a. most of the particles passed straight through the foil.

b. some particles were slightly defl ected.

c. a few particles bounced straight back.

d. All of the above

9 Which of the following determines the identity of an element?

a. atomic numberb. mass numberc. atomic massd. overall charge

0 Isotopes exist because atoms of the same element can have different numbers of

a. protons.b. neutrons.c. electrons.d. None of the above

Short Answer

q What force holds electrons in atoms?

w In two or three sentences, describe Thomson’s plum-pudding model of the atom.

UNDERSTANDING KEY IDEAS

USING KEY TERMS


ANSWERS

Using Key Terms1. Protons2. protons3. Neutrons4. mass number5. atomic mass

Understanding Key Ideas6. c7. a8. d9. a

10. b11. electromagnetic force12. Sample answer: The plum-

pudding model describes the atom as a lump of positively charged material with nega-tively charged particles throughout. The positively charged material is like the pudding, and electrons are like plums in the pudding.

Assignment GuideSECTION QUESTIONS

1 6, 8, 12, 17–18

2 1–5, 7, 9–11, 13–16, 19–21

a b

c

Math Skills

e Calculate the atomic mass ofgallium, which consists of 60%gallium-69 and 40% gallium-71.

r Calculate the number of protons,neutrons, and electrons in an atomof zirconium-90 that has no overallcharge and an atomic number of 40.

tConcept Mapping Use the followingterms to create a concept map: atom,nucleus, protons, neutrons, electrons, iso-topes, atomic number, and mass number.

yAnalyzing Processes Particle accelera-tors, such as the one below, are devicesthat speed up charged particles inorder to smash them together. Scien-tists use these devices to make atoms.How can scientists determine whetherthe atoms formed are a new elementor a new isotope of a known element?

uAnalyzing Ideas John Dalton made anumber of statements about atomsthat are now known to be incorrect.Why do you think his atomic theoryis still found in science textbooks?

iAnalyzing Methods If scientistshad tried to repeat Thomson’sexperiment and found that theycould not, would Thomson’sconclusion still have been valid?Explain your answer.

Use the diagrams below to answer thequestions that follow.

o Which diagrams represent isotopesof the same element?

p What is the atomic number for A?

a What is the mass number for B?

INTERPRETING GRAPHICS

CRITICAL THINKING

CHAPTER RESOURCES


CRF • Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg

Workbooks

Study Guide• Study Guide is also available in Spanish.

13. (0.60 � 69 amu) � (0.40 �71 amu) � 69.8 amu

14. number of protons � atomicnumber � 40number of neutrons � massnumber � atomic number � 50number of electrons � numberof protons � 40

Critical Thinking15. An answer to this

exercise can befound at the backof this book.

16. Scientists must determine theatomic number, or the numberof protons, in the newly formednucleus. The nucleus is that ofa new element only if the num-ber of protons is different fromall known elements.

17. Sample answer: Dalton’s atomictheory was the first one basedon experimental evidence. Ithelps show how a theory de-velops as new information isdiscovered.

18. No, the results of an experimentmust be repeatable to be con-sidered valid.

Interpreting Graphics19. a and c20. 321. 7

Chapter 11 • Chapter Review 329

READING

Passage 1 In the Bohr model of the atom, electrons can be found only in certain energy levels. Electrons “jump” from one level to the next level without passing through any of the regions in between. When an electron moves from one level to another, it gains or loses energy, depending on the direction of its jump. Bohr’s model explained an unusual event. When electric charges pass through atoms of a gaseous element, the gas produces a glowing light, like in a neon sign. If this light is passed through a prism, a pat-tern of lines appears, each line having a different color. The pattern depends on the element—neon has one pattern, and helium has another. In Bohr’s model, the lines are caused by electron jumps from higher to lower energy levels. Because only certain jumps are possible, electrons release energy only in certain quantities. These “packets” of energy produce the lines that are seen.

1. In the Bohr model of the atom, what limitation is placed on electrons?

A the number of electrons in an atomB the electrons’ being found only in certain

energy levelsC the size of electronsD the speed of electrons

2. What causes the colored lines that appear when the light from a gas is passed through a prism?

F packets of energy released by electron jumps

G electrons changing colorH atoms of the gas exchanging electronsI There is not enough information to

determine the answer.

Passage 2 No one has ever seen a living dinosaur, but scientists have determined the appearance of Tyrannosaurus rex by studying fossilized skeletons. Scientists theorize that these extinct creatures had big hind legs, small front legs, a long, whip-like tail, and a mouth full of dagger-shaped teeth. However, theories of how T. rex walked have been harder to develop. For many years, most scientists thought that T. rex plodded slowly like a big, lazy lizard. However, after studying well-preserved dinosaur tracks and noticing skeletal similarities between certain dinosaur fossils and living creatures like the ostrich, many scientists now theorize that T. rex could turn on the speed. Some scientists estimate that T. rex had bursts of speed of 32 km/h (20 mi/h)!

1. According to this passage, where does most of what we know about the appearance of Tyrannosaurus rex come from?

A fossilized skeletonsB dinosaur tracksC living organisms such as the ostrichD living specimens of T. rex

2. How did scientists conclude that T. rex could probably move very quickly?

F They measured the speed at which it could run.

G They compared fossilized T. rex tracks with T. rex skeletons.

H They studied dinosaur tracks and noted similarities between ostrich skeletons and T. rex skeletons.

I They measured the speed at which ostriches could run.

Read each of the passages below. Then, answer the questions that follow each passage.

READING

MISCONCEPTIONALERT

Passage 11. B2. F

Question 2: A certain amount of information synthesis is required to arrive at the exact wording of answer F. The second-to-last sentence of the passage makes a direct connection between released energy and jumps made between energy levels by electrons. The last sentence of the passage names the quantities of energy released as “packets.”

Passage 21. A2. H Question 2: Answer F may tempt students who

think that the given speed of 32 km/h must be a measurement. Scientists studied T. rex skeletons and footprints but did not compare one with the other, so answer G is incorrect. Answer H correctly states the reason given in the passage: analysis of dinosaur tracks and comparison of T. rex skeletons with skeletons of ostriches. It may be reasonable to infer that ostriches run at about 32 km/h, but that reason alone is not what made scientists think that T. rex could run quickly, so answer I is incorrect.

Answers to the standardized test preparation can help you identify student misconcep-tions and misunderstandings.

Teacher’s NoteTeacher’s NoteTo provide practice under more realistic testing conditions, give students 20 minutes to answer all of the questions in this Standardized Test Preparation.


Standardized

Test Preparatio

n

1. The black circles in the center of the model represent neutrons. What do the white circles in the center represent?

A electronsB protonsC nucleiD atoms

2. What is the mass number of the atom shown in the model?

F 3G 7H 9I 11

3. What is the overall charge of the atom shown in the model?

A �2B �1C 0D �1

1. Aimee, Mari, and Brooke are 163 cm, 171 cm, and 175 cm tall. Which of the following measurements is a reasonable average height of these three friends?

A 170 cmB 175 cmC 255 cmD 509 cm

2. A certain school has 40 classrooms. Most of the classrooms have 25 to 30 students. Which of the following is a reasonable estimate of the number of students that go to this school?

F 40 studentsG 100 studentsH 1,100 studentsI 2,000 students

3. Jenna is setting up a fi sh tank in her room. The tank is the shape of a rectangular prism. The height of the tank is 38 cm, the width is 23 cm, and the length is 62 cm. The tank is fi lled with water to a point that is 7 cm from the top. How much water is in the tank?

A 44,206 cm3

B 48,070 cm3

C 54,188 cm3

D 64,170 cm3

4. Which of the following is equal to 85?

F 8 � 8 � 8 � 8 � 8G 5 � 5 � 5 � 5 � 5 � 5 � 5 � 5H 5 � 8I 8 � 8 � 8 � 8 � 8

Use the diagram of an atom below to answer the questions that follow.

Read each question below, and choose the best answer.

INTERPRETING GRAPHICS MATH

Chapter 11 • Standardized Test Preparation 331

INTERPRETING GRAPHICS1. B2. G3. C

Question 1: Protons and neutrons are the only particles in the nucleus, so if the black circles are neutrons, the white circles must be protons.

Question 2: Mass number is the total number of protons and neutrons in an atom, which in this case is 7. Mass number is not to be confused with atomic number, which is just the number of protons.

Question 3: There are four protons and four electrons in the atom shown. Each proton has a positive charge, and each electron has a negative charge, so the total charge of the atom shown is �4 � 4 � 0.

MATH1. A2. H3. A4. I

Question 3: Correctly answering this question requires that the student subtract 7 from the height of the tank to calculate the volume of water. The vol-ume is then (38 cm � 7 cm) � 23 cm �62 cm � 44,206 cm3. It may be helpful to use a box as a three-dimensional model in order to show students how to correctly answer this question.

CHAPTER RESOURCES


CRF • Standardized Test Preparation g

State Resources

For specifi c resources for your state, visit go.hrw.com and type in the keyword HSMSTR.

in Action

in Action

Language ArtsWrite a paragraph in which you rephrase the information above

in your own words. Be sure to include what helium-3 is, where it can be found, and how it could be used.

MathIf you split apart an atom of lead (atomic number � 82) and one of the atoms left was gold (atomic number � 79), what would be the atomic number of the other atom that resulted from this change?

WRITINGSKILL

Weird ScienceMining on the Moon?Since the end of the Apollo moon mis-sions in 1972, no one has set foot on the surface of the moon. But today, an isotope of helium known as helium-3 is fueling new interest in returning to the moon. Some sci-entists speculate that helium-3 can be used as a safe and nonpolluting fuel for a new kind of power plant. Helium-3 is very rare on Earth, but a huge amount of the isotope exists on the surface of the moon. But how can helium-3 be brought to Earth? Some researchers imagine a robotic lunar mining operation that will harvest the helium-3 and transport it to Earth.

Scientific DiscoveriesModern AlchemyHundreds of years ago, many people thought that if you treated lead with certain chemicals, it would turn into gold. People called alchemists often spent their whole lives trying to find a way to make gold from other metals, such as lead. We now know that the methods alchemists tried to change one element to another did not work. But in the 20th century, scientists learned that you really could change one element to another! In a nuclear reaction, small particles can be collided with atomic nuclei. This process makes the nuclei split apart to form two nuclei of different elements.

Scientific Discoveries

BackgroundThe modern-day science of chemistry can be traced to the practice of alchemy, which was common in the 17th century and earlier. Alchemists devised experimental techniques and apparatus that remained valu-able after alchemical theory had been discredited.

Weird Science

Discussion--------------------------------------a

Tell students that the United Nations has declared that no country can lay claim to the moon or the resources that exist there. However, the rule does not apply to private companies. Ask students: “Do you think pri-vate companies should be allowed to own mining rights on the moon? Explain.”

Answer to Math Activity

atomic number of other new atom �82 � 79 � 3

Answer to Language Arts Activity

Accept all reasonable responses.


Social Studies

Find out about an experimen-

tal physicist who made an important discovery. Write a one-page report about how that discovery affected the ideas of other scientists.

Melissa FranklinExperimental Physicist In the course of a single day, you could find experimental physicist Melissa Franklin running a huge drill or showing her lab to a 10-year-old child. You could see her putting together a huge piece of electronic equipment or even telling a joke. Then you’d see her really get down to business—studying the smallest particles of matter in the universe.

“I am trying to understand the forces that describe how everything in the world moves—especially the smallest things,” Franklin explains. Franklin and her team helped discover a particle called the top quark. (Quarks are the tiny particles that make up protons and neutrons.) “You can understand the ideas without having to be a math genius,” Franklin says. “Anyone can have ideas,” she says, “absolutely anyone.” Franklin also has some advice for young people interested in phys-ics. “Go and bug people at the local university. Just call up a physics per-son and say, ‘Can I come visit you for a couple of hours?’ Kids do that with me, and it’s really fun.”

To learn more about these Science in Action topics, visitgo.hrw.com and type in thekeyword HP5ATSF.

Check out Current Science®

articles related to this chapter by visiting go.hrw.com. Just type in the keyword HP5CS11.

WRITINGSKILL

Chapter 11 • Science in Action 333

Careers

BackgroundAn experimental physicist is dif-ferent from a theoretical physi-cist. Theoretical physicists deal with formulas, calculations, and predictions. Experimental physi-cists, such as Franklin, test the theories developed by other scientists. Often, experimental physicists must build machines and develop new technologies to test their theories.

A person who wants to pursue a career in physics will find it important to study science and mathematics in high school. In college, physics students study chemistry and higher math-ematics in addition to physics. Most people who have careers in physics have advanced degrees.

Teaching Strategy-- GENERAL

Invite a physicist to speak to your class. Many colleges, uni-versities, and community col-leges have programs that make professors available for such visits. Prior to the visit, help your students develop questions to ask your speaker.

Discussion------------------------------------- GENERAL

Talk about the difference between a theoretical physicist and an experimental physicist. Have students discuss which type of physicist they might like to be and why. Have them dis-cuss which type of scientist, if either, is more important and why they think so.

Answer to Social Studies Activity

Reports should focus on an important scien-tist from any era and a single discovery that changed how other scientists thought about some aspect of the physical world.

hst physical science teachers editions5ebeba82addad021.jimcontent.com/download/version/...crf...

Documents