Transcript The Structure of an Atom

The Structure of
an Atom
I.
A.
Three Main Parts to the Atom
Nucleus
1)
Protons
a.
Positive Charge (+)
b.
# of Protons = Atomic
Number
2)
Neutrons
a.
No charge (neutral)
b.
# Neutrons = Atomic Mass minus
the Atomic Number
B. Electrons
1)
Negative Charge (-)
2)
# Electrons = # Protons =
Atomic #
General Rules about Electrons
1.
The electrons “live” in
different energy levels
around the nucleus
2.
An energy level “shell” must
be filled before adding
another energy level.
a)
b)
c)
1st Energy Level (Closest to the
nucleus) can only have 2
electrons
2nd Energy Level = Maximum of 8
electrons
3rd Energy Level
1. If the 3rd shell is the outer
shell then 8 electrons
maximum.
2.
3.
If the 3rd shell is not the outer shell
then it must have at least 8
electrons but not more than 18
electrons.
4th Energy Level
If the 4th shell is the outer shell
then 8 electrons maximum.
3) Valence Electrons: The number of
electrons in the outer energy level. These
electrons are used in chemical bonds.
The End