7.2 Oxidation States and Rules for Assigning Oxidation States

This topic explains oxidation states (also called oxidation numbers) and the rules used to assign them to atoms in compounds and ions.

Definition

Oxidation state or oxidation number is defined as the number of charges an atom will have in a molecule or a compound.

Simple explanation: Oxidation state tells you how many electrons an atom has lost, gained, or shared in a compound.

Main Idea

• The elements that show an increase in oxidation number are oxidized.
• The elements that show a decrease in oxidation number are reduced.

Simple explanation: Oxidation state helps us track which element is oxidized and which is reduced in a redox reaction.