Oxidation Number Method
The oxidation number method, also called oxidation states, keeps track of electrons gained when a substance is reduced and the electrons lost when a substance is oxidized. Each atom in a neutral molecule or charged species is assigned an oxidation number. When there is an increase in the oxidation number, oxidation occurs. When there is a decrease in the oxidation number, reduction occurs. The sum of all the oxidation numbers in a compound is equal to its overall charge.