Other notations are currently favoured due to the ambiguity of the term valence. Apart from the Stock system of oxidation states (also known as oxidation numbers) and the lambda notation used in the IUPAC nomenclature of inorganic chemistry, the oxidation state is a more precise description of the electronic state of atoms in a molecule.The number of valence electrons gained or lost by an atom in a molecule is determined by its oxidation state. The oxidation state, unlike the valency number, can be positive (for an electropositive atom) or negative (for an electronegative atom) (for an electronegative atom).