The Structure of the Atom 43

Name Date

The Structure of the AtomBefore You Read

scientific law

theory

element

law of definite proportions

law of multipleproportions

Define the following terms.

describes a relationship in nature that is supported by many

experiments

an explanation supported by many experiments; is still subject to

new experimental data, can be modified, and is considered

successful if it can be used to make predictions that are true

a pure substance that cannot be separated into simpler substances

by physical or chemical means

states that regardless of the amount, a compound is always

composed of the same elements in the same proportion by mass

states that when different compounds are formed by a combination

of the same elements, different masses of one element combine with

the same mass of the other element in a ratio of small whole numbers

Describe three things that you already know about the atom.

1. Accept all reasonable responses.

2.

3.

ReviewVocabulary

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44 Early Theories of Matter

Name Date

Dalton’s atomic theory

atom

accurate

conclude

reveal

The Structure of the AtomSection 4.1 Early Theories of Matter

Scan Section 1 of your text. Use the checklist below as a guide.

• Read all section titles.

• Read all boldfaced words.

• Read all tables and graphs.

• Look at all pictures and read the captions.

• Think about what you already know about this subject.

List three things you expect to learn about while reading the section.

1. Accept all reasonable responses.

2.

3.

Use your text to define each term.

a theory proposed by John Dalton in 1808, based on numerous

scientific experiments, which marked the beginning of the

development of modern atomic theory

the smallest particle of an element that retains the properties of

the element

Define the following term.

having a measured value close to the accepted value

making a judgment based on the information obtained

to make something known

NewVocabulary

AcademicVocabulary

Main Idea Details

I&E 1.d, 1.k, 1.n

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The Structure of the Atom 45

Name Date

The PhilosophersUse with pages 87–89.

John DaltonUse with pages 89–90.

Summarize the effect that Aristotle had on the atomic theory proposed by Democritus.

Aristotle rejected Democritus’ ideas because it did not agree with his ideas

on nature. He did not believe that the “nothingness” of empty space could

exist. He denied the existence of atoms. People accepted Aristotle’s

conclusions for 2,000 years, and the ideas of Democritus were not developed.

List the main points of Dalton’s atomic theory.

1. All matter is composed of extremely small particles called atoms.

2. All atoms of a given element are identical in size, mass, and

chemical properties. Atoms of one element are different from

those atoms of any other element.

3. Atoms cannot be created, divided into smaller particles, or

destroyed.

4. Different atoms combine in simple whole-number ratios to form

compounds.

5. In a chemical reaction, atoms are separated, combined, or

rearranged.

Discuss Dalton’s ideas by completing the following paragraph.

After years of studying , Dalton was able to

accurately determine the of the elements involved

in the reactions. His conclusions resulted in the ,

which helped to explain that in chemical reactions

separate, , or , but are not created,

, or .divideddestroyed

rearrangecombine

atoms

atomic theory

mass ratios

chemical reactions

Section 4.1 Early Theories of Matter (continued)

Main Idea Details

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46 Early Theories of Matter

Name Date

Defining theAtom

Use with pages 90–91.

Compare and contrast the atomic theories of Democritus andDalton. Mark an X under each name if a statement in the tableapplies to that person’s theory.

Section 4.1 Early Theories of Matter (continued)

Main Idea Details

Explain an atom by completing the following statements.

The atom is the

.

When a group of atoms and act as a

, the result is known as a .moleculeunit

bond together

of the element

smallest particle that retains the properties

Statement Democritus Dalton

All matter is made of tiny pieces. X X

Matter is made of empty space through which atoms move.

X

Atoms cannot be divided. X X

Atoms cannot be created. X X

Atoms cannot be destroyed. X X

Different atoms combine in Xwhole-number ratios to form

compounds.

The properties of atoms varybased on shape, size, andmovement.

X

Different kinds of atoms comein different sizes and shapes.

X

The experiments of the alchemistsrevealed the properties of some metals and provided the foundation for the science ofchemistry. Although not successful, alchemy proved beneficial to science. Explain howthis example can be applied to modern research.

Accept all reasonable responses. Possible answer: Even research and experiments that do

not succeed add to our body of knowledge and provide useful information to later

researchers.

REAL-WORLD CONNECTION

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The Structure of the Atom 47

Name Date

cathode ray

electron

nucleus

proton

neutron

concentrate

The Structure of the AtomSection 4.2 Subatomic Particles and the Nuclear Atom

Scan Section 2 of your text. Use the checklist below as a guide.

• Read all section titles.

• Read all boldfaced words.

• Read all tables and graphs.

• Look at all pictures and read the captions.

• Think about what you already know about this subject.

Write three facts you discovered about subatomic particles.

1. Accept all reasonable responses.

2.

3.

Use your text to define each term.

ray of radiation emitting from the cathode end of a tube used by

researchers to study mass and charge

negatively charged particles that are part of all forms of matter

tiny, dense, centrally located region within the atom that contains all of

an atom’s positive charge and virtually all of its mass

a subatomic particle carrying a charge equal to but opposite that of an

electron; that is, a positive charge of 1+

a subatomic particle with a mass nearly equal to that of a proton,

but that has no electrical charge

Define the following term.

to build up or combine substances at one location or into one mass

NewVocabulary

AcademicVocabulary

Main Idea Details

Chemistry 1.e, 1.h, 11.g; I&E 1.n

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48 Subatomic Particles and the Nuclear Atom

Name Date

Discovering theElectron

Use with pages 92–94.

Summarize the information you learned from cathode ray experi-ments. Use Figure 4-8 for reference.

Section 4.2 Subatomic Particles and the Nuclear Atom (continued)

Main Idea Details

Identify the major discoveries about subatomic particles made bythe 19th century.

1. Cathode rays were actually a stream of charged particles.

2. The particles carried a negative charge.

3. There were particles smaller than atoms.

Altering the gas in the

tube and the material

used for the

cathode have no effect.

Proves: Proves:

Indicates:

Particles in the ray

are part of all matter.

Cathode ray is

deflected in a

magnetic field.

Cathode ray is deflected

toward the positively

charged plate by an

electric field.

Cathode Ray

Experiment

Cathode rays have a

negative charge.

Cathode ray is composed of charged particles.

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The Structure of the Atom 49

Name Date

The Nuclear AtomUse with pages 94–95.

Completing theAtom—The

Discovery ofProtons and

NeutronsUse with pages 96–97.

Describe Rutherford’s model of the atom by completing the follow-ing statements.

1.Most of an atom consists of moving

through .

2.The electrons are within the atom by their

to the positively charged .

3.The volume of through which the electrons move

is many times than the volume of the .

Organize the properties of subatomic particles by completing thetable below. Use Table 4-1 for reference.

nucleuslarger

space

nucleus

attractionheld

empty space

rapidlyelectrons

Section 4.2 Subatomic Particles and the Nuclear Atom (continued)

Main Idea Details

Summarize what you have learned about subatomic particles bycompleting the following paragraph.

Atoms have a shape. The of an atom

is made up of that have a positive charge and

that have no . The nucleus makes up

of the mass of an atom. Most of an is

made up of negatively charged traveling around the

charged nucleus. The are held in place

by their to the positive charge of the .

The of the protons and neutrons are almost to

each other while the of the electrons is .extremely smallmass

equalmass

nucleusattraction

electronspositively

electrons

atom99.97%

chargeneutrons

protons

nucleusspherical

Electron Proton Neutron

Symbol e� p� n0

Location surrounding in nucleus in nucleusthe nucleus

Relativeelectrical 1� 1� 0charge

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