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Welcome to Welcome to AtomsAtoms

This is a This is a Self-GuidedSelf-Guided lesson on lesson on AtomsAtoms. In this computer activity . In this computer activity

you will be creating your own you will be creating your own Study Study GuideGuide..

Feel free to complete this lesson at Feel free to complete this lesson at your own pace. your own pace.

Please follow all instructions Please follow all instructions carefully. carefully.

Ask your teacher if you need any Ask your teacher if you need any helphelp..

Atoms Part 1Atoms Part 1In In Part 1Part 1 of this of this activity you will activity you will learn about the learn about the

Atomic - Molecular Atomic - Molecular Theory of Matter.Theory of Matter. You will also learn You will also learn about scientists about scientists

and how they have and how they have gathered evidence gathered evidence

about atoms.about atoms.

Please complete Please complete your Study Guide your Study Guide as you proceed! as you proceed!

Atomic - Molecular Atomic - Molecular Theory of MatterTheory of Matter

The The Atomic - Molecular Atomic - Molecular Theory of MatterTheory of Matter states states

that all matter is that all matter is composed of small, composed of small,

fast moving particles fast moving particles called atoms. These called atoms. These

atoms can join atoms can join together to form together to form

molecules. molecules.

This theory is really This theory is really thousands of individual thousands of individual theories that provide theories that provide

evidence for the whole evidence for the whole theory.theory.

MatterMatterSince the atom is Since the atom is too small to be too small to be seen even with seen even with

the most the most powerful powerful

microscopes, microscopes, scientists rely scientists rely

upon models to upon models to help us to help us to

understand the understand the atom.atom.

Believe it or not this is a Believe it or not this is a microscope. Even with the microscope. Even with the world’s best microscopes world’s best microscopes we cannot clearly see the we cannot clearly see the

structure or behavior of the structure or behavior of the atom.atom.

Scientific ModelsScientific Models Scientists create Scientists create models to help them models to help them to visualize complex to visualize complex

properties, properties, structures or structures or

behaviors. Since the behaviors. Since the atom is so small, atom is so small, scientists must scientists must gather gather Indirect Indirect

EvidenceEvidence to develop to develop their models.their models.

This is a model of a very This is a model of a very complex molecule made of complex molecule made of

many different kinds of many different kinds of atoms. Each colored ball atoms. Each colored ball represents an atom of a represents an atom of a

different element.different element.

What should a Model look What should a Model look like?like?

Scientific models Scientific models may not always may not always

look like the look like the actual object. A actual object. A

model is an model is an attempt to use attempt to use

familiar ideas to familiar ideas to describe describe

unfamiliar things unfamiliar things in a visual way.in a visual way.

This is a painting of a young This is a painting of a young woman by Pablo Picasso. Does woman by Pablo Picasso. Does

it actually look like a young it actually look like a young woman?woman?

Is this really an Atom?Is this really an Atom?

The model above represents The model above represents the most modern version of the most modern version of

the atom. the atom.

(Artist drawing(Artist drawing)

Many of the models that you Many of the models that you have seen may look like the one have seen may look like the one

below. It shows the parts and below. It shows the parts and structure of the atom. Even structure of the atom. Even

though we do not know what an though we do not know what an atom looks like, scientific atom looks like, scientific models must be based on models must be based on

evidence. evidence.

Indirect EvidenceIndirect EvidenceIndirect Evidence is evidence Indirect Evidence is evidence gathered without being able to gathered without being able to

directly observe the object. The directly observe the object. The Atomic - Molecular Theory of MatterAtomic - Molecular Theory of Matter

is based upon a vast amount of is based upon a vast amount of indirect evidence gathered over a indirect evidence gathered over a

long period of time. Just like pieces long period of time. Just like pieces being added to a puzzle, each new being added to a puzzle, each new bit of information gives us a better bit of information gives us a better

understanding of atoms.understanding of atoms.

How can Indirect How can Indirect Evidence be Gathered?Evidence be Gathered?

Click here to visit a lClick here to visit a lab where actual scieab where actual scientific research on atntific research on atoms is conducted.oms is conducted.

Answer the Answer the questions in your questions in your Study Guide about Study Guide about

the example of the example of Indirect Evidence.Indirect Evidence.

Can a Model be Can a Model be Changed?Changed?

A model can be changed as A model can be changed as new information is collected. new information is collected.

From the early Greek concept From the early Greek concept to the modern atomic theory, to the modern atomic theory, scientists have built upon and scientists have built upon and modified existing models of modified existing models of

the atom.the atom.

Where did it all Where did it all begin?begin?

The word “atom” The word “atom” comes from the comes from the

Greek word Greek word ““atomos”atomos” which which

means means indivisibleindivisible..

The idea that all The idea that all matter is made up matter is made up of atoms was first of atoms was first proposed by the proposed by the

Greek philosopher Greek philosopher DemocritusDemocritus in the in the 5th century B.C5th century B.C..

History of the History of the AtomAtom

The concept of atoms as proposed The concept of atoms as proposed by Democritus remained by Democritus remained

relatively unchanged for over relatively unchanged for over 2,000 years. Beginning in the 2,000 years. Beginning in the

late 18th century new late 18th century new discoveries were made that led discoveries were made that led

to a better understanding of to a better understanding of atoms and chemistry. Many atoms and chemistry. Many

scientists since that time have scientists since that time have contributed new evidence for contributed new evidence for

the Atomic - Molecular Theory. the Atomic - Molecular Theory.

ClickClick on the picture of on the picture of Niels BohrNiels Bohr to visit a website to learn more to visit a website to learn more about important scientists and about important scientists and

how our models of the atom how our models of the atom have changed.have changed.

Niels Bohr is one of Niels Bohr is one of many scientists that many scientists that

have given us a have given us a better understanding better understanding

of Atoms.of Atoms.

You have finished Part 1 You have finished Part 1 of this program. See the of this program. See the teacher for the materials teacher for the materials

to begin Part 2.to begin Part 2.

GOOD JOB!GOOD JOB!

Atoms Part 2Atoms Part 2In In Part 2Part 2 of this of this activity you will activity you will learn about the learn about the particles within particles within the atom. You the atom. You will visit more will visit more

websites to learn websites to learn about the about the

structure and structure and behavior of the behavior of the

atom.atom.

Check your Study Check your Study Guide for Guide for

Instructions!Instructions!

Atomic StructureAtomic Structure NucleusNucleus - the central portion of - the central portion of

the atom. Contains the protons the atom. Contains the protons and neutrons.and neutrons.

Electron CloudElectron Cloud - area around the - area around the nucleus where electrons are nucleus where electrons are found. Electrons are arranged found. Electrons are arranged within the electron cloud in energy within the electron cloud in energy levels. (Energy levels are levels. (Energy levels are sometimes called shells or orbits).sometimes called shells or orbits).

Subatomic Subatomic ParticlesParticles

ProtonProton - positive charged particle - positive charged particle found in the nucleus. Mass = 1 found in the nucleus. Mass = 1 amu. amu. (A.M.U - Atomic Mass Unit)(A.M.U - Atomic Mass Unit)

Neutron Neutron - particle with no - particle with no charge. Found in the nucleus. charge. Found in the nucleus. Mass = 1 amu. Mass = 1 amu.

ElectronElectron - negative charged - negative charged particle found within the electron particle found within the electron

cloud .cloud . Mass = 1/1836 amu.Mass = 1/1836 amu.

Why are all Atoms are Why are all Atoms are Electrically Neutral?Electrically Neutral?

IMPORTANTIMPORTANTIn all In all ATOMSATOMS the number the number

of positively charged of positively charged protons is always equal protons is always equal

to the number of to the number of negatively charged negatively charged

electrons.electrons.

Normally in an atom Normally in an atom the number of the number of

electrons within the electrons within the electron cloud is electron cloud is

equal to the number equal to the number of protons in the of protons in the

nucleus. The positive nucleus. The positive and negative charges and negative charges

cancel each other cancel each other out. Therefore, the out. Therefore, the

atom is said to be atom is said to be electrically neutralelectrically neutral. .

If an atom gains or loses If an atom gains or loses electrons the atom is no electrons the atom is no longer neutral . This can longer neutral . This can

happen if the atom happen if the atom absorbs or releases absorbs or releases

energy The atom is then energy The atom is then called an called an IONION..

Make a Make a diagram diagram of the of the HeliumHelium atom in atom in

your your Study Study Guide.Guide.

Now you are off to Now you are off to TV Land!TV Land!

Now you will visit a Now you will visit a website to learn website to learn

about Atomic about Atomic Structure. Be sure Structure. Be sure

to follow the to follow the instructions in your instructions in your

Study Guide.Study Guide. Click here to visit a website at PBS (Public Broadcasting System)

“You know - the station Sesame Street “You know - the station Sesame Street and Mr. Rogers are on.”and Mr. Rogers are on.”

IsotopesIsotopes All atoms of an element have All atoms of an element have

the same number of protons the same number of protons but the number of neutrons but the number of neutrons can vary. Atoms with the can vary. Atoms with the

same number of protons and same number of protons and differing numbers of differing numbers of neutrons are called neutrons are called

ISOTOPES.ISOTOPES. Some Isotopes are unstable. Some Isotopes are unstable.

The nucleus of unstable The nucleus of unstable atoms do not hold together atoms do not hold together well. well. Radioactive decayRadioactive decay is is the process whereby the the process whereby the

nucleus of unstable isotopes nucleus of unstable isotopes release fast moving particles release fast moving particles

and energy.and energy.

The discovery of The discovery of Radioactivity almost Radioactivity almost

happened by accident. happened by accident. Click on the picture of Click on the picture of

Henri BecquerelHenri Becquerel to learn to learn about his discovery.about his discovery.

You have now You have now completed the completed the

AtomsAtoms PowerPoint.PowerPoint. See the teacher for See the teacher for further instructions.further instructions.

Great Job!!Great Job!!