Inorganic compound with the formula FeO
Chemical compound

Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite.[3][4] 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.[5]

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 iron(III) oxide (Fe2O3). A similar procedure can also be used for the synthesis of manganous oxide and stannous oxide.[6][7]

Stoichiometric FeO can be prepared by heating Fe0.95O with metallic iron at 770 °C and 36 kbar.[8]

Reactions

FeO is thermodynamically unstable below 575 °C, tending to disproportionate to metal and Fe3O4:[5]

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 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.[8]

In contrast to the crystalline solid, in the molten state iron atoms are coordinated by predominantly 4 or 5 oxygen atoms.[9]

Below 200 K there is a minor change to the structure which changes the symmetry to rhombohedral and samples become antiferromagnetic.[8]

Occurrence in nature

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.[10]

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.

See also

References

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ "404 - School of Art & Design" (PDF). art.illinois.edu. {{cite web}}: Cite uses generic title (help)
  3. ^ "Wüstite". www.mindat.org.
  4. ^ "List of Minerals". www.ima-mineralogy.org. March 21, 2011.
  5. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  6. ^ 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.
  7. ^ Practical Chemistry for Advanced Students, Arthur Sutcliffe, 1930 (1949 Ed.), John Murray - London
  8. ^ a b c Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford University Press ISBN 0-19-855370-6
  9. ^ Shi, Caijuan; Alderman, Oliver; Tamalonis, Anthony; Weber, Richard; You, Jinglin; Benmore, Chris (2020). "Redox-structure dependence of molten iron oxides". Communications Materials. 1: 80. doi:10.1038/s43246-020-00080-4.
  10. ^ "Science Jan 2012". Archived from the original on January 24, 2012.

External links