1. S + Na Na2S Na More Ionic Bonding 2Na+1
Ionic bonding involves the electrical attraction of a cation (+) and an anion (-).
Charges and amounts of atoms balance to become a neutral compound. Na S + -2
2Na+1
Na2S Na

2. OXIDATION Example: Na0 Na+1 + 1e- By losing electrons
Process of an element becoming more POSITIVE.
How does element oxidize?
By losing electrons
Example: Na Na e-
The ionic charge of Na (0 or +1) can also be called its oxidation number.

3. REDUCTION By Gaining electrons Example: S0 + 2e- S-2
Process of an element becoming more NEGATIVE.
How does element reduce?
By Gaining electrons
Example: S0 + 2e S-2
What’s the oxidation number for S? -2

4. Parts of an Equation: Putting it all together
REACTANTS OXIDATION NUMBER
PRODUCTS COEFFICIENT
SUBSCRIPT
Example:
2Na+1 S -2
Na2S +
*Cation is always written first!
*Atoms combine in simplest whole number ratios to make their charges zero.

5. PRACTICE
1. Write oxidation / reduction equations for Potassium and Oxygen.
K0  K e (oxidation)
O0 + 2e-  O (reduction)
2. Write the combined equation for potassium and oxygen when they form an ionic bond.
2 K O-2  K2O

6. Na + F [Na]+ + [ F ]- Remember this? Lewis Structures in an equation!
Brackets needed for IONS !!!!!

7. Polyatomic ions Ions can get a bit more complex…….
A group of atoms that bond together to form
a larger charged particle.
This many atom particle acts as ONE and
bonds with other particles to cancel out
all charges!

8. Polyatomic ions Formula Charge Name SO4-2 2- sulfate SO3-2 sulfite
NO3-1 1-
nitrate
NO2-1
nitrite
OH-1
hydroxide
NH4+1 1+
ammonium
PO4-3 3-
phosphate
C2H3O2-1
acetate
CN-1
cyanide

9. Lewis Structures can be drawn for
Polyatomic Ions, also: N H +1 O -1

10. 3Na+1 + PO4-3  Na3PO4 The making of Sodium Phosphate:
Why are 3 sodium ions required ?
To balance the -3 charge of the phosphate

11. Ca+2 + 2C2H3O2-1  Ca(C2H3O2)2 The making of Calcium Acetate
When multiple numbers of polyatomic ions are
needed to cancel out charges, they are put
in parentheses.

12. PRACTICE Write balanced equations and formulas for the
following compounds:
Aluminum Hydroxide
Ammonium Nitride
Calcium Sulfite
Barium Cyanide
Al OH-1  Al (OH)3
3NH N-3  (NH4)3N
Ca SO3-2  Ca2(SO3)2 
CaSO3
Ba CN-1  Ba(CN)2