Oxidation Numbers

Part of Unit 4 of AP Chemistry

Oxidation Numbers - Number of electrons an atom can donate or accept to form a bond with another atom

Rules §

1. The oxidation number of any uncombined element is 0
2. The oxidation number of a monoatomic ion equals the charge on the ion
3. The more electronegative element in a binary compound is assigned the number equal to the charge it would have if it were an ion
4. The oxidation number of fluorine in a compound is always -1
5. Oxygen has an oxidation number of -2 unless it is combined with F (when it is +2) or it is in a peroxide (such as H${}_2$O${}_2$ or Na${}_2$O${}_2$), when it is -1
6. Oxidation state of Hydrogen in most of it’s compounds is +1 unless it is combined with a metal, in which case it’s -1
7. In compounds, elements of groups 1 and 2 as well as aluminum have oxidation numbers of +1, +2, and +3 respectively
8. The sum of the oxidation numbers of all atoms in a neutral compound is 0
9. The sum of the oxidation number of all atoms in a polyatomic ion equals the charge of the ion

Oxidation - The process of losing electrons Reduction - The process of gaining electrons Oxidizing Agent - The substance that gains electrons Reducing Agent - The substance that loses electrons