Iron(II) oxide or ferrous oxide is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the formula FeO. Its mineral form is known as wüstite. One of several

iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...

s, it is a black-colored powder that is sometimes confused with rust, the latter of which consists of hydrated

iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally ...

(ferric oxide). Iron(II) oxide also refers to a family of related non-stoichiometric compounds, which are typically iron deficient with compositions ranging from Fe_0.84O to Fe_0.95O.

Preparation

FeO can be prepared by the thermal decomposition of iron(II) oxalate. :FeC₂O₄ → FeO + CO₂ + CO The procedure is conducted under an inert atmosphere to avoid the formation of

(Fe₂O₃). A similar procedure can also be used for the synthesis of

manganous oxide Manganese(II) oxide is an inorganic compound with chemical formula MnO.Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. It forms green crystals. The compound is produced on a large s ...

and

stannous oxide Tin(II) oxide (stannous oxide) is a compound with the formula SnO. It is composed of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form. Preparation and reactions Blue ...

. Stoichiometric FeO can be prepared by heating Fe_0.95O with metallic iron at 770 °C and 36 kbar.Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford University Press

Reactions

FeO is thermodynamically unstable below 575 °C, tending to disproportionate to metal and Fe₃O₄: :4FeO → Fe + Fe₃O₄

Structure

Iron(II) oxide adopts the cubic, rock salt structure, where iron atoms are octahedrally coordinated by oxygen atoms and the oxygen atoms octahedrally coordinated by iron atoms. The non-stoichiometry occurs because of the ease of oxidation of Fe^II to Fe^III effectively replacing a small portion of Fe^II with two thirds their number of Fe^III, which take up tetrahedral positions in the close packed oxide lattice. In contrast to the crystalline solid, in the molten state iron atoms are coordinated by predominantly 4 or 5 oxygen atoms. Below 200 K there is a minor change to the structure which changes the symmetry to rhombohedral and samples become antiferromagnetic.

Occurrence in nature

Iron(II) oxide makes up approximately 9% of the Earth's

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

. Within the mantle, it may be electrically conductive, which is a possible explanation for perturbations in Earth's rotation not accounted for by accepted models of the mantle's properties.

Uses

Iron(II) oxide is used as a pigment. It is FDA-approved for use in cosmetics and it is used in some tattoo inks. It can also be used as a phosphate remover from home aquaria.

References

External links

Wustite Mineral Data
{{oxygen compounds Iron(II) compounds Iron oxide pigments Non-stoichiometric compounds Transition metal oxides Rock salt crystal structure Glass dyes