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Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite.<ref name=Mindat>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=IMA>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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). Iron(II) oxide also refers to a family of related non-stoichiometric compounds, which are typically iron deficient with compositions ranging from Fe0.84O to Fe0.95O.<ref name = "Greenwood">Template:Greenwood&Earnshaw</ref>
PreparationEdit
FeO can be prepared by the thermal decomposition of iron(II) oxalate.
The procedure is conducted under an inert atmosphere to avoid the formation of iron(III) oxide (Template:Chem2). A similar procedure can also be used for the synthesis of manganous oxide and stannous oxide.<ref>H. Lux "Iron (II) Oxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1497.</ref><ref>Practical Chemistry for Advanced Students, Arthur Sutcliffe, 1930 (1949 Ed.), John Murray - London</ref>
Stoichiometric FeO can be prepared by heating Fe0.95O with metallic iron at 770 °C and 36 kbar.<ref name = "Wells">Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford University Press Template:ISBN</ref>
ReactionsEdit
FeO is thermodynamically unstable below 575 °C, tending to disproportionate to metal and Fe3O4:<ref name="Greenwood" />
StructureEdit
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 FeII to FeIII effectively replacing a small portion of FeII with two-thirds their number of FeIII, which take up tetrahedral positions in the close packed oxide lattice.<ref name="Wells" />
In contrast to the crystalline solid, in the molten state iron atoms are coordinated by predominantly 4 or 5 oxygen atoms.<ref name="ShiFeOx2020">Template:Cite journal</ref>
Below 200 K there is a minor change to the structure which changes the symmetry to rhombohedral and samples become antiferromagnetic.<ref name="Wells" /><ref>Template:Cite book</ref>
Occurrence in natureEdit
Iron(II) oxide makes up approximately 9% of the Earth's mantle. 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
UsesEdit
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.
See alsoEdit
ReferencesEdit
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Template:Iron compounds Template:Oxides Template:Molecules detected in outer space Template:Oxygen compounds