Iron(II) oxide has three primary uses. First, it has long been used as a dye or pigment in pottery, glazes, and glasses, especially in the green, heat-absorbing glass used in buildings, automobiles, and other applications. The compound is also used as a raw material in the production of steel.

Why is FeO the molecular formula for iron (II) oxide? FeO is the molecular formula for iron (II) oxide. Because iron forms more than one cation, or positive ion, the Roman numeral II is used to distinguish it from the iron (III) cation.

Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite. One of several iron oxides, it is a black-colored powder that is sometimes confused with rust, the latter of which consists of hydrated iron(III) oxide (ferric oxide).

FeO ionic bond | SSHADE.