1. Review – Atoms and Isotopes
What is the definition of atom?
What is the definition of isotope?

2. Now, how are these atoms similar? How are they different?

3. Ion
Definition
An atom in which the number of electrons does NOT equal the number of protons causing it to have a net positive or negative charge.

4. Cation Anion 2 Types of Ions Lost electrons Gained electrons
Positive charge
Negative charge
p+ > e-
p+ < e-

5. Why do atoms form ions?
Neutral atoms seek stability by gaining and losing valence electrons to satisfy the:
Octet rule – Group A elements tend to combine in a way that each atom has 8 valence electrons so that they have electron configurations similar to a noble gas.

6. Examples Cation (+) Anion (-) Phosphorus # Valence e-? Lewis Dot?
Calcium
# Valence e-?
Lewis Dot?
Gain/Lose e-?
How many?
Ion Notation
Phosphorus
# Valence e-?
Lewis Dot?
Gain/Lose e-?
How many?
Ion Notation 2 5 Ca P
Lose
Gain 2 3
Ca+2
P-3

7. Practice 1. Beryllium 2. Fluorine 3. Sulfur 4. Hydrogen 5. Oxygen
Element
Valence Electrons
Lewis Dot
Gain/Lose e-? How many?
Ion Notation
1. Beryllium
2. Fluorine
3. Sulfur
4. Hydrogen
5. Oxygen
6. Gallium
7. Nitrogen
8. Cesium
9. Aluminum
10. Iodine
Be+2
F-1
S-2
H+1
O-2
Ga+3
N-3
Cs+1
Al+3
I-1

8. Naming Ions Positive ions keep their name
Ex. Sodium ion (Na+)
Negative ions end with suffix –ide
Ex. Chloride ion (Cl-)