1. Oxidation Number This is a signed (+ or –) number that indicates the actual charge or the apparent charge that an atom of an element would have in a particular situation.

2. Rules for Assigning Oxidation Numbers Rule #1: The oxidation number of a free element is zero (0).

3. Rules for Assigning Oxidation Numbers Rule #2: The oxidation number of a monatomic ion is equal to the charge on the ion.

4. Rules for Assigning Oxidation Numbers Rule #3: The oxidation number of hydrogen when in a compound is +1; except when combined with a metal, then it is – 1.

5. Rules for Assigning Oxidation Numbers Rule #4: The oxidation number of oxygen when in a compound is – 2; except when it would violate other rules, then it is – 1.

6. Rules for Assigning Oxidation Numbers Rule #5: The oxidation numbers of the atoms of a compound must add up to zero (0).

7. Rules for Assigning Oxidation Numbers Rule #6: The oxidation numbers of the atoms of a polyatomic ion must add up to equal the charge on the ion.

8. Rules for Assigning Oxidation Numbers Rule #7: The oxidation numbers of Group IA elements in a compound is always +1; Group IIA elements in a compound always have an oxidation of +2; Group VIIA elements when written last in a binary compound will always have an oxidation number of – 1.