4The oxidation number of oxygen in most compound is-2,but in peroxides(过氧化物) oxygen can have an oxidation number of-1 Oxygen can also have positive oxidation numbers when combined with fluorine.For example,the oxidation number of oxygen is +2 in OF2 and +1 in O2F2.④The oxidation number of oxygen in most compound is –2; but in peroxides(过氧化物) oxygen can have an oxidation number of –1. Oxygen can also have positive oxidation numbers when combined with fluorine. For example, the oxidation number of oxygen is +2 in OF2 and +1 in O2F2