Oxidation state, also known as oxidation number, is a concept used in chemistry to describe the charge that an atom would have if all its bonds were ionic. It is a measure of the degree of oxidation of an atom in a compound. The oxidation state of an atom can be positive, negative, or zero, and is determined based on the number of electrons that an atom has gained or lost in a chemical reaction. Understanding the oxidation state of atoms in a compound is important in determining how they will react with other substances and in predicting their chemical properties.