In sodium bromide, NaBrO3, the oxidation state of sodium is 1+, bromide is 5+, and oxygen is 2-. The oxidation states in a molecule are important when it comes to understanding the oxidation-reduction reactions that occur in a chemical reaction. In oxidation, there is an increase in oxidation numbers whereas in reduction, oxidation states decrease.
The oxygen atom in most compounds has an oxidation state of 2- and Group 1 metals, such as sodium, have an oxidation state of 1+. Since the oxidation state in the molecule must add up to zero, the oxidation state of bromide can be easily calculated by (2 x 3 – 1).