Oxidation Number

In coordination chemistry, the oxidation number of a central atom in a coordination compound is the charge that it would have if all the ligands were removed along with the electron pairs that were shared with the central atom.

The oxidation number is used in the nomenclature of inorganic compounds. It is represented by a Roman numeral. The oxidation number is placed either as a right superscript to the element symbol, for example FeIII, or in parentheses after the name of the element, iron(III): in the latter case, there is no space between the element name and the oxidation number.