Oxidation state

Hypothetical charge of an atom if all its bonds to different atoms were fully ionic

In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom assuming all of its bonds to other atoms are fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero.

From Wikipedia, under CC BY-SA. More on occurri.