1. Oxidation Numbers These rules are seriously easy!!

2. Rule 1 The oxidation number for an atom of any free (uncombined) element is ZERO. (eg: Na, Ca, Br 2 have an oxidation number of 0 )

3. Rule 2 The oxidation number for a simple single atom (ie monatomic) ion is the charge on the ion. (eg Cl - = -1, Na + = +1)

4. Rule 3 In non metal hydrogen containing compounds, oxidation number of hydrogen is +1 (eg HCl, H 2 O). In metal hydrides, the oxidation number of hydrogen is -1 (eg NaH, LiH, CaH 2.).

5. Rule 4 Oxygen is usually assigned an oxidation number of -2 when combined. (eg H 2 O, CO 2, Na 2 O) When combined in peroxides (eg H 2 O 2, or Na 2 O 2 ) it has an oxidation number of -1. When combined with F, ie in F 2 O, oxygen has an oxidation number of +2.

6. Rule 5 The sum of oxidation numbers of all the atoms in the formula for a neutral compound is ZERO.

7. Rule 6 The sum of oxidation numbers of a polyatomic ion is the same as the charge on that ion.