Definition of Oxidation State
Oxidation state also is known as oxidation number is the total number of electrons that is gained or lost by an atom when it is going to form a chemical bond with another atom. All the atoms are assigned an oxidation number when they are taking part in an oxidation-reduction reaction. This tells us about the capability of the atom to either donate, gain, or share the electrons.
The ion of oxygen generally has an O2- oxidation state which reflects that it has an ability to donate two electrons. On the other hand, if an ion has a positive oxidation number like Fe3+, it can gain 3 electrons. The sum of oxidation number is zero for the neutral molecules. For-example: Fe2O3.