How to find Oxidizatotion number of …

An oxidation number can be assigned to a given element or compound by following the following rules.

• Any free element has an oxidation number equal to zero.
• For monoatomic ions, the oxidation number always has the same value as the net charge corresponding to the ion.
• The hydrogen atom (H) exhibits an oxidation state of +1. However, when bonded with an element with less electronegativity than it, it exhibits an oxidation number of -1.
• Oxygen has an oxidation of -2 in most of its compounds. However, in the case of peroxides, the oxidation number corresponding to oxygen is -1.
• All alkali metals (group 1 elements) have an oxidation state of +1 in their compounds.
• All alkaline earth metals (group 2 elements) exhibit an oxidation state of +2 in their compounds.
• In the compounds made up of two elements, a halogen (group 17 elements) have an oxidation number of -1 assigned to them.
• In the case of neutral compounds, the sum of all the oxidation numbers of the constituent atoms totals to zero.
• When polyatomic ions are considered, the sum of all the oxidation numbers of the atoms that constitute them equals the net charge of the polyatomic ion.

Thus, the oxidation number of an atom in a given compound can be calculated with the steps mentioned above.