Editing Iron(II) oxide

{{short description|Inorganic compound with the formula FeO}}
{{Chembox
| Watchedfields  = changed
| verifiedrevid  = 477163416
| ImageFile1     = Iron(II) oxide.jpg
| ImageSize1     = 
| ImageName1     = Iron(II) oxide
| ImageFile2     = Manganese(II)-oxide-xtal-3D-SF.png
| ImageSize2     = 
| IUPACName      = Iron(II) oxide
| SystematicName = 
| OtherNames     = Ferrous oxide, Iron monoxide, Wüstite
| Section1       = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 14237
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = G7036X8B5H
| InChI = 1/Fe.O/rFeO/c1-2
| InChIKey = UQSXHKLRYXJYBZ-WPTVXXAFAB
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 50820
| SMILES = [Fe]=O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Fe.O
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = UQSXHKLRYXJYBZ-UHFFFAOYSA-N
| CASNo = 1345-25-1
| CASNo_Ref = {{cascite|correct|CAS}}
| EINECS = 
| PubChem = 14945
| RTECS = 
| Gmelin = 13590
 }}
| Section2       = {{Chembox Properties
| Formula = FeO
| MolarMass = 71.844 g/mol
| Appearance = black crystals
| Density = 5.745 g/cm<sup>3</sup>
| MeltingPtC = 1377
| MeltingPt_ref = <ref>Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, {{ISBN|0-07-049439-8}}</ref>
| BoilingPtC = 3414
| BoilingPt_notes = 
| Solubility = Insoluble
| SolubleOther = insoluble in [[alkali]], [[ethanol|alcohol]] <br> dissolves in [[acid]]
| Solvent = 
| pKa = 
| pKb = 
| RefractIndex = 2.23
| MagSus = {{val|+7200|e=-6|u=cm3/mol}}
 }}
| Section3       = {{Chembox Structure
| CrystalStruct = 
| Coordination = 
 }}
| Section4       = {{Chembox Thermochemistry
| DeltaHf = 
| DeltaHc = 
| Entropy = 
| HeatCapacity = 
 }}
| Section7       = {{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0793.htm ICSC 0793]
| MainHazards = can be combustible under specific conditions<ref>{{Cite web|url=https://art.illinois.edu/images/documents/MSDS/Metals/Ferric-Oxide.pdf|title=Ferric(ous) Oxide, Black |website=art.illinois.edu |archive-url=https://web.archive.org/web/20190511223604/https://art.illinois.edu/images/documents/MSDS/Metals/Ferric-Oxide.pdf |archive-date=11 May 2019 |url-status=dead}}</ref>
| NFPA-H = 1
| NFPA-F = 1
| NFPA-R = 0
| FlashPt = 
| AutoignitionPtC = 200
| ExploLimits = 
| PEL = 
 }}
| Section8       = {{Chembox Related
| OtherAnions = [[Iron(II) sulfide]]<br>[[Iron(II) selenide]]<br>[[Iron(II) telluride]]
| OtherCations = [[Manganese(II) oxide]]<br>[[Cobalt(II) oxide]]
| OtherFunction  = [[Iron(II,III) oxide]]<br>[[Iron(III) oxide]]
| OtherFunction_label = [[Iron]] [[oxide]]s
| OtherCompounds = [[Iron(II) fluoride]]
 }}
}}

'''Iron(II) oxide''' or '''ferrous oxide''' is the [[inorganic compound]] with the formula FeO.  Its mineral form is known as [[wüstite]].<ref name=Mindat>{{Cite web|url=https://www.mindat.org/min-4316.html|title=Wüstite|website=www.mindat.org}}</ref><ref name=IMA>{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=March 21, 2011|website=www.ima-mineralogy.org}}</ref> One of several [[iron oxide]]s, 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 compound]]s, which are typically iron deficient with compositions ranging from Fe<sub>0.84</sub>O to Fe<sub>0.95</sub>O.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref>

==Preparation==
FeO can be prepared by the thermal decomposition of [[iron(II) oxalate]].
:{{chem2|FeC2O4 -> FeO + CO2 + CO}}
The procedure is conducted under an inert atmosphere to avoid the formation of iron(III) oxide ({{chem2|Fe2O3}}).  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 Fe<sub>0.95</sub>O with metallic iron at 770&nbsp;°C and 36&nbsp;kbar.<ref name = "Wells">Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford University Press {{ISBN|0-19-855370-6}}</ref>

==Reactions==
FeO is thermodynamically unstable below 575&nbsp;°C, tending to disproportionate to metal and [[iron(II,III) oxide|Fe<sub>3</sub>O<sub>4</sub>]]:<ref name="Greenwood" />
:{{chem2|4 FeO -> Fe + Fe3O4}}

==Structure==
[[Iron]](II) oxide adopts the cubic, [[sodium chloride|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<sup>II</sup> to Fe<sup>III</sup> effectively replacing a small portion of Fe<sup>II</sup> with two-thirds their number of Fe<sup>III</sup>, 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">{{cite journal |last1=Shi |first1=Caijuan |last2=Alderman |first2=Oliver |last3=Tamalonis |first3=Anthony |last4=Weber |first4=Richard |last5=You |first5=Jinglin |last6=Benmore |first6=Chris |title=Redox-structure dependence of molten iron oxides |journal=Communications Materials |date=2020 |volume=1 |issue=1 |page=80 |doi=10.1038/s43246-020-00080-4 |bibcode=2020CoMat...1...80S |doi-access=free }}</ref>

Below 200&nbsp;K there is a minor change to the structure which changes the symmetry to rhombohedral and samples become [[antiferromagnetism|antiferromagnetic]].<ref name="Wells" /><ref>{{Cite book |date=2017 |title= Proceedings of the 5th Unconventional Resources Technology Conference|url=http://dx.doi.org/10.15530/urtec-2017-2670073 |location=Tulsa, OK, USA |publisher=American Association of Petroleum Geologists |doi=10.15530/urtec-2017-2670073|isbn= 978-0-9912144-4-0}}</ref>

==Occurrence in nature==
Iron(II) oxide makes up approximately 9% of the Earth's [[mantle (geology)|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>{{Cite web|url=http://news.sciencemag.org/sciencenow/2012/01/electric-material-in-mantle-coul.html?ref=hp|archiveurl=https://web.archive.org/web/20120124011327/http://news.sciencemag.org/sciencenow/2012/01/electric-material-in-mantle-coul.html?ref=hp|url-status=dead|title=''Science'' Jan 2012|archivedate=January 24, 2012}}</ref>

==Uses==
Iron(II) oxide is used as a [[pigment]]. It is [[Food and Drug Administration|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 also==
* [[Iron(II) hydroxide]]
* [[Iron(II)]]

==References==
{{reflist}}

==External links==
* [http://webmineral.com/data/Wustite.shtml Wustite Mineral Data]
{{Iron compounds}}
{{Oxides}}
{{Molecules detected in outer space}}
{{oxygen compounds}}

[[Category:Iron(II) compounds]]
[[Category:Iron oxide pigments]]
[[Category:Non-stoichiometric compounds]]
[[Category:Transition metal oxides]]
[[Category:Rock salt crystal structure]]
[[Category:Glass dyes]]