Oxidation Number

The oxidation number of an atom is the number of electrons it gains or loses in forming a compound.• the oxidation number of uncombined elements is zero and for an ion is the charge on the ion• the sum of oxidation numbers of all elements in a neutral compound is zero.• the more electronegative element is given a negative oxidation number.• in compounds, fluorine is always -1; hydrogen is +1 (except when bonded to a less electronegative element, as in metal hydrides, when it is -1); oxygen is -2 (except -1 in peroxides and positive with fluorine).