Oxidation State
The oxidation state is a measure of the degree of oxidation (the loss of an electron by a molecule, atom or ion) of an atom in a chemical compound. It is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are represented by Arabic numerals, and are always associated with a sign (positive or negative) unless zero. Thus, a hydrogen ion, which is nothing more than a proton, would have an oxidation state of 1+.
The increase in oxidation state of an atom is known as an oxidation: a decrease in oxidation state is known as a reduction (gain of an electron by a molecule, atom or ion). Such reactions involve the transfer of electrons, a net gain in electrons being a reduction and a net loss of electrons being an oxidation.