oxidation number, oxidation state(noun)

the degree of oxidation of an atom or ion or molecule; for simple atoms or ions the oxidation number is equal to the ionic charge

"the oxidation number of hydrogen is +1 and of oxygen is -2"

oxidation number(Noun)

The net sum of the negative, less the positive, charges on an atom.

Oxidation number

Oxidation number is used in the nomenclature of inorganic compounds where it is represented by a Roman numeral. In older literature the term is referred to as Stock number, however the use of this term is no longer recommended. Oxidation number represents the degree of oxidation of an element in a substance. This degree of oxidation is, with the exception of coordination compounds where a different definition applies, the imaginary charge on the atom if the substance were broken down into ions. The oxidation number in compound naming is placed either as a right superscript to the element symbol in chemical formula, for example FeIII, or in parentheses after the name of the element, iron in chemical names. For example Fe2(SO4)3 would be named iron sulfate and its formula could be shown as FeIII2(SO4)3. This is because a sulfate ion has a charge of -2, so each iron atom takes a charge of +3. Note that fractional oxidation numbers should not be used in naming. In coordination chemistry, the oxidation number of a coordination compound is the charge that the central atom would possess if all the ligands were removed along with the electron pairs that were shared with the central atom.