What' is oxidation number

Answer 1

'Oxidation number' and oxidation state are often used interchangeably.

Oxidation state is a formal way of determining the degree of oxidation of an atom or ion or molecule; for ions the oxidation number is equal to the ionic charge. In non ionic compounds the most electronegative element is assumed to "own" the electrons. So in say InP which is a semiconductor and not ionic, the oxidation state of indium is +III and P is -III.

Oxidation number is a convention used in complexes. Ligands are removed from the ion with all bonding electrons. Often the oxidation number and oxidation state have the same values but calculating the the oxidation number of N in ammonia, H is removed as hydride ion, H- you get the strange looking result of nitrogen with an oxidation number of +3. In contrast the oxidation states of N and H would be calculated as -III and +1

Answer 2

An oxidation number refers to a number that is assigned to an element to represent quantity of lost or gained electrons.