S = +6
The oxidation number of a free element is always 0.The oxidation number of a monatomic ion equals the charge of the ion.Fluorine in compounds is always assigned an oxidation number of -1.The alkali metals (group I) always have an oxidation number of +1.The alkaline earth metals (group II) are always assigned an oxidation number of +2.Oxygen almost always has an oxidation number of -2, except in peroxides (H2O2) where it is -1 and in compounds with fluorine (OF2) where it is +2.Hydrogen has an oxidation number of +1 when combined with non-metals, but it has an oxidation number of -1 when combined with metals.The algebraic sum of the oxidation numbers of elements in a compound is zero.The algebraic sum of the oxidation states in an ion is equal to the charge on the ion.