Hmmmm…Imagine cutting a gold bar in half.Then cut in half again.

…and again.…and again.

…and again.…and again.

Speak up! Could you keep cutting that bar in half forever? Why or why not?

How small could you cut up that gold and it still be gold?

8th Grade Physical Science

Atoms

Introduction to AtomsAn Atom Apart Reading/Highlighting Guide

1. According to the text, what are atoms?2. What does the Greek word a’tomos mean?3. What are atoms made of?4. What decides the chemical element of an

atom?5. What determines the chemical properties

of an atom?

Introduction to Atoms• What is an atom?• An atom is the smallest particle into which

an element can be divided and still be the same substance.

• Atoms make up elements and elements combine to form compounds.

Introduction to Atoms• What is an atom?• An atom is made of 3 parts:• Protons (+)• Neutrons (neutral)• Electrons (-)

• Protons and neutrons make up the nucleus of the atom

• Electrons orbit around the nucleus like planets around the sun*

*Actually this is not true but it is a useful analogy

Introduction to Atoms• Key terms:• Valence electron – electrons farthest from

the nucleus (involved in bonding)• Atomic number* = number of protons.

*Determines the identity of an element • Mass number = # of protons + # of neutrons• Atomic mass = the average mass of all the

known isotopes of an element

Drawing Atoms• Even though it is not quite accurate anymore,

the Bohr model of the atom is still useful for building a basic understanding of atoms.

Drawing AtomsPractice:

Draw an atom and label its parts. Your drawing should include:• 3 Protons (+)• 3 Neutrons (neutral)• 3 Electrons (-)• Nucleus

Your drawing should fill an entire page!

Drawing AtomsDivide your page as shown and draw an atom of each of the following elements.

Helium atom Beryllium atom

Carbon atomBoron atom

Atomic Summary• Cold calls…

1. What are the three subatomic particles in an atom? (Be sure to include their charges!)

2. What 2 subatomic particles are in the nucleus of an atom?3. Where are electrons found in an atom?4. What determines the chemical element of an atom?5. What is a valence electron?6. What is the difference between atomic mass and mass

number?7. What is the charge of the nucleus? Why?8. What is the charge of the atom as a whole? Why?

Drawing AtomsDivide your page as shown and draw an atom of each of the following elements.

Speak Up! Compare and contrast the atoms pictured below

Drawing AtomsQuick Quiz: Draw and label an atom of the element nitrogen.