-ous

Name:
-ous
Detailed information:
A suffix, used in naming inorganic compounds, that indicates that the central element is present in its lower oxidation state. For example, in ferrous chloride (FeCl₂), the iron atom is in its lower oxidation state of +2, equivalent to its valence; in an ionized state it would have two positive charges (Fe²⁺). (A recommended change in this system of nomenclature is to use the common name of the element [iron] together with a Roman numeral showing the oxidation number; thus, ferrous chloride would be iron(II) chloride.)