Assigning Oxidation Numbers

Free elements

Elements in their natural state have an oxidation number of 0.

Diatomic Ions

Ions composed of two atoms have an oxidation number of 0.

Ions of one atom

Ions consisting of a single atom have an oxidation number equal to their charge.

Neutral compound

The sum of oxidation numbers in a neutral compound is 0.

Polyatomic ion

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

Metals

Metals typically exhibit a positive oxidation number.

Nonmetals

Nonmetals can display positive or negative oxidation numbers depending on the compound they form.

Hydrogen

Hydrogen commonly has an oxidation number of +1.