* The oxidation number of an atom in an elementary substance is 0. This means that the oxidation number of an O atom in O2 is 0.
* The oxidation number of a Group IA atom in any compund is +1; The oxidation number of a Group IIA atom in any compound is +2.
* The oxidation number of fluorine is -1 in all of its compounds.
* The oxidation number of chlorine, bromine, and iodine is -1 in any compound containing only two elements.
* The usual oxidation number of oxygen in a compound is -2. The major exceptions of this rule are peroxides, like H2O2, which have an oxidation number of -1.
* The oxidation number of hydrogen in most compounds is +1.
* The sum of the oxidation numbers in a compound is always zero. For something that is an ion consisting of two atoms (a polyatomic ion), the oxidation numbers add up to the charge on the ion.
How to find oxidation number on redox reactions
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