The oxidation number of any uncombined element is 0

(e.g. Cl2 has an oxidation number of 0)

The oxidation number of a monoatomic ion equals the charge on the ion

(e.g. Na+ has an oxidation number of 1+)

The more electronegative compound in a binary compound is assigned the number equal to the charge it would have if it were an ion

(e.g. KCl has oxidation numbers of 1+ and 1- respectively)

The oxidation number of fluorine in a compound is always 1-

(e.g. F2O has oxidation numbers of 1- and 2+ respectively)

Oxygen has an oxidation state of 2- unless it is combined with F (when it is 2+) or it is in a peroxide (such as H2O2 or Na2O2), when it is 1-

(e.g. H2O has oxidation numbers of 1+ and 2- respectively)

The oxidation state of hydrogen in most of its compounds is 1+ unless it is combined with a metal, in which case it is 1-

(e.g. CaH3 has oxidation numbers of 3+ and 1- respectively)

In compounds the elements of groups 1 and 2 as well as aluminum have oxidation numbers of 1+, 2+ and 3+ respectively

(e.g. CaCl2 has oxidation numbers of 2+ and 1- respectively)

The sum of the oxidation numbers of all atoms in a neutral compound combines to 0

The sum of the oxidation numbers of all atoms in a polyatomic ion equals the charge of the ion

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