Rules for determining oxidation numbers. The oxidation number of any free element is zero , regardless of how complex the allotrope may be. The oxidation number for any simple, monatomic ion is equal to the charge of the ion. The sum of all the oxidation numbers of the atoms in a molecule or polyatomic ion must be equal to the charge of the substance. In its compounds, fluorine has an oxidation number of -1 5.
Examples Find the oxidation numbers of all of the species present in the following compounds.