1. Atomic Structure
Nucleus
Protons
Neutrons
Electrons

2. Atomic Structure Electrons Tiny, very light particles
Have a negative electrical charge (-)
Move around the outside of the nucleus

3. Atomic Structure Protons Much larger and heavier than electrons
Protons have a positive charge (+)
Located in the nucleus of the atom 

4. Atomic Structure Neutrons Large and heavy like protons
Neutrons have no electrical charge
Located in the nucleus of the atom 

5. Atomic Structure

6. Describing Atoms Atomic Number = number of protons
In a neutral atom, the # of protons = the # of electrons

7. Describing Atoms
Atomic Mass Number - equal to the number of protons plus neutrons.

8. Describing Atoms
Atomic Weight - average mass of the naturally occurring isotopes of an element .