Iron(II) oxide or ferrous oxide is the
inorganic compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''.
Inorgan ...
with the formula FeO. Its mineral form is known as
wüstite.
One of several
iron oxide
An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.
Iron ...
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 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.
:
The procedure is conducted under an inert atmosphere to avoid the formation of iron(III) oxide (). A similar procedure can also be used for the synthesis of
manganous oxide and
stannous oxide.
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:
:
Structure
Iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
(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. 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
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
. 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
*
Iron(II) hydroxide
*
Iron(II)
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