atoms: simplest form of matter

7/27/2019 ATOMS: Simplest form of Matter

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Atoms You will learn about

the Atomic -

Molecular Theory of Matter. You will alsolearn about scientists

and how they havegathered evidence

about atoms.

Please complete your Study Guide as you

proceed!



Atomic - MolecularTheory of Matter

The Atomic - Molecular Theory of Matter states

that all matter is

composed of small, fastmoving particles calledatoms. These atomscan join together to

form molecules.

This theory is reallythousands of individualtheories that provide

evidence for the whole

theory.



Matter Since the atom is

too small to be seen

even with the mostpowerful

microscopes,

scientists rely uponmodels to help us to

understand the

atom.

Believe it or not this is amicroscope. Even with the

world’s best microscopes wecannot clearly see the

structure or behavior of the

atom.



Scientific Models Scientists create

models to help themto visualize complex

properties,structures or

behaviors. Since the

atom is so small,scientists mustgather Indirect

Evidence to develop

their models.

This is a model of a verycomplex molecule made of

many different kinds of atoms.Each colored ball represents an

atom of a different element.



What should a Model look like?

Scientific modelsmay not always

look like the

actual object. Amodel is an

attempt to use

familiar ideas todescribeunfamiliar thingsin a visual way.

This is a painting of a young womanby Pablo Picasso. Does it actually

look like a young woman?



Is this really an Atom?

The model above representsthe most modern version of

the atom.

(Artist drawing)

Many of the models that you haveseen may look like the one below. Itshows the parts and structure of theatom. Even though we do not know

what an atom looks like, scientificmodels must be based on evidence.



Indirect Evidence Indirect Evidence is evidence gathered

without being able to directly observe

the object. The Atomic - Molecular Theory of Matter is based upon a vastamount of indirect evidence gatheredover a long period of time. Just like

pieces being added to a puzzle, eachnew bit of information gives us abetter understanding of atoms.



How can Indirect Evidencebe Gathered?

Answer the questionsin your Study Guideabout the example

of Indirect Evidence.



Can a Model be Changed?

A model can be changed as newinformation is collected.

From the early Greek concept tothe modern atomic theory,

scientists have built upon andmodified existing models of theatom.



Where did it all begin?

The word “atom” comes from the

Greek word

“ atomos” whichmeans indivisible .

The idea that allmatter is made up of

atoms was firstproposed by the

Greek philosopherDemocritus in the5th century B.C.



History of the Atom The concept of atoms as proposed by

Democritus remained relativelyunchanged for over 2,000 years.

In the late 18th century newdiscoveries were made that led to

a better understanding of atomsand chemistry. Many scientists

since that time have contributednew evidence for the Atomic -

Molecular Theory.

Click on the picture of Niels Bohr tovisit a website to learn more

about important scientists andhow our models of the atom have

changed.

Niels Bohr is one of many scientists that

have given us a betterunderstanding of

Atoms.

http://www.crocodile-clips.com/absorb/AC4/sample/LR301.html



You have learned enough in

the First Part of theLesson! Now let’s proceed

to the Second Part.

Good JOB!



Atoms You will learn

about the particles

within the atom. You will visit morewebsites to learn

about the structureand behavior of the

atom.

Check your Study Guide for

Instructions!



Atomic Structure

Nucleus - the central portion of theatom. Contains the protons and

neutrons.Electron Cloud - area around the

nucleus where electrons are found.

Electrons are arranged within theelectron cloud in energy levels(Energy levels are sometimes

called shells or orbits).



Subatomic Particles

Proton - positive charged particlefound in the nucleus. Mass = 1

amu. (a.m.u - Atomic Mass Unit) Neutron - particle with no

charge. Found in the nucleus.

Mass = 1 amu.Electron - negative charged

particle found within the electron

cloud . Mass = 1/1836 amu.



Why are all Atoms are

Electrically Neutral?

IMPORTANT

In all ATOMS the number of positively charged protons

is always equal to thenumber of negatively

charged electrons.

Normally in an atom thenumber of electronswithin the electron

cloud is equal to thenumber of protons in

the nucleus. Thepositive and negative

charges cancel eachother out. Therefore,the atom is said to beelectrically neutral .

If an atom gains or loseselectrons the atom is nolonger neutral . This can

happen if the atom absorbs orreleases energy The atom is

then called an ION .



Make adiagram

of the

Helium atom in

yourStudyGuide.



Isotopes All atoms of an element have

the same number of protonsbut the number of neutronscan vary. Atoms with the

same number of protons anddiffering numbers of neutrons

are called ISOTOPES.

Some Isotopes are unstable.The nucleus of unstable atoms

do not hold together well.Radioactive decay is the

process whereby the nucleusof unstable isotopes release

fast moving particles and

energy.

The discovery of Radioactivityalmost happened by accident.Click on the picture of HenriBecquerel to learn about his

discovery.

http://www.chem.duke.edu/~jds/cruise_chem/nuclear/discovery.html



You have now

completed the Atoms Lesson.

Great Job!!



PREPARED BY:

JOHN CHESTER

VICTORIANO

&

DARLYN JHANE

ROSARITO

atoms: simplest form of matter

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