Oxidation State - Oxidation Number

The terms oxidation state and oxidation number are often used interchangeably. However, oxidation number is used in coordination chemistry with a slightly different meaning. In coordination chemistry, the rules used for counting electrons are different: Every electron in a metal-ligand bond belongs to the ligand, regardless of electronegativity. Also, oxidation numbers are conventionally represented with Roman numerals, while oxidation states use Indo-Arabic numerals.