The Difference Between Oxidation State and Oxidation Number

In most cases, oxidation state and oxidation number are used interchangeably.
In most cases, oxidation state and oxidation number are used interchangeably. iStock Vectors, Getty Images

Oxidation state and oxidation number are quantities that commonly equal the same value for atoms in a molecule and are often used interchangeably. Most of the time, it doesn't matter if the term oxidation state or oxidation number is used.

There is a slight difference between the two terms.

Oxidation state refers to the degree of oxidation of an atom in a molecule. Each atom of the molecule will have a distinct oxidation state for that molecule where the sum of all the oxidation states will equal the overall electrical charge of the molecule or ion.

Each atom is assigned an oxidation state value based on predetermined rules based on electronegativity and periodic table groups.

Oxidation numbers are used in coordination complex chemistry. They refer to the charge the central atom would have if all ligands and electron pairs shared with the atom were removed.