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Iron II Oxide Formula

Last Updated : 23 Jul, 2025

Iron (II) Oxide is an inorganic compound that has one iron atom and one oxygen atom. Iron 2 Oxide is also called Ferrous Oxide or Iron Monoxide. The Iron II Oxide chemical formula is FeO. It is a crystalline solid and it does not dissolve in water and alkali but is soluble in acids.

In this article, we will learn about the Iron 2 Oxides Formula, Iron 2 Oxide Structure, Uses of Iron II Oxide, Health Hazards of Iron II Oxide, and others in detail.

Iron II Oxide(FeO) Formula

Iron (II) Oxide belongs to a family of related non-stoichiometric compounds and is made up of iron and oxygen elements. There are various types of iron oxide, and iron II oxide is one of them. Iron (II) oxide is an ionic compound that is also known as ferrous oxide or iron monoxide. FeO is the chemical or molecular formula of Iron (II) Oxide, i.e., it consists of one iron atom and one oxygen atom. Around 9% of the Earth's crust is made up of iron (II) oxide. Iron (II) oxide occurs as a black crystalline solid, that is widely used to make pigments and dyes used for pottery glazes. A light blue/green crystal is formed when iron II oxide comes in contact with water. Iron II oxide easily oxidizes due to air. It dissolves in acids but is not soluble in water and alkali. It quickly absorbs carbon dioxide and forms Iron(II) Carbonate (FeCO3) which also happens to be a strong base.

Structure of Iron II Oxide(FeO)

Iron (II) oxide is present in a mineral called Wustite that has an octahedral crystal lattice, like that of rock salt. Iron 2 oxide has a cubic, rock salt structure, with iron atoms being octahedrally coordinated by oxygen atoms and oxygen atoms being octahedrally coordinated by iron atoms. The structure of Iron II Oxide is added in the image below,

👁 Iron Oxide structure
Iron Oxide structure

Preparation of Iron (II) Oxide

Iron 2 Oxide occurs naturally as a result of the incomplete oxidation of the metal.

2Fe + O2 → 2FeO

It is synthetically prepared by the thermal decomposition of iron (II) oxalate, which creates iron (II) oxide, carbon dioxide, and carbon monoxide. This procedure has to be conducted under an inert atmosphere so that the formation of iron (III) oxide (Fe2O3) can be avoided.

FeC2O4 → FeO + CO2 + CO

Properties of Iron II Oxide(FeO)

Physcial Properties of the Iron 2 Oxide (FeO) is added in the table below,

Chemical formula FeO
Molar Mass  71.844 g/mol
Density  5.745 g/cm3
Appearance 

Solid at room temperature (Black crystals)

Solubility
  • Insoluble in Water and Alkali
  • Soluble in Acids
Boiling point  3,414 °C
Melting point  1,377 °C
Magnetic Susceptibility+7200.10−6 cm3/mol
Refractive Index2.23

Chemical Properties of Iron II Oxide(FeO)

Various Chemical Properties of Iron II Oxide(FeO) are added below,

  • Below 575 °C, FeO is thermodynamically unstable and tends to be disproportionate to metals and Fe3O4.

4FeO → Fe + Fe3O4

  • It easily gets oxidized if exposed to air and produces iron(III) oxide.

4FeO + O2 → 2Fe2O3

  • Iron II Oxide (FeO) dissolves in sulphuric acid (H2SO4) and forms Iron (III) sulfate or ferric sulfate.

2FeO + 4H2SO4 → Fe2(SO4)3 +4H2O + SO2

  • Iron 2 Oxide (FeO) dissolves in nitric acid (HNO3) and forms Ferric nitrate or Iron (III) nitrate.

3FeO + 10HNO3 → 5H2O + NO + 3Fe(NO3)3

  • Iron 2 Oxide (FeO) reacts with hydrogen chloride (HCl) and produces Iron(II) chloride and water.

FeO + 2HCl → FeCl2 + H2O

  • Iron II Oxide (FeO) reacts with silver nitrate(AgNO3) and produces Silver oxide and Ferrous Nitrate.

2AgNO3 + FeO → Ag2O + Fe(NO3)2

Uses of Iron(II) Oxide{FeO}

Various uses of FeO are,

  • Iron 2 oxide is used as a pigment, and dyes are used for pottery glazes. 
  • It is used in cosmetics and is used in some tattoo inks. 
  • It is used as a raw material to produce the steel that is used to construct buildings and manufacture cars. 
  • In its green crystallized form, it is a component of the heat-absorbing glass that is used in automobiles and buildings.
  • It is used as a catalyst in industrial operations.
  • It can also be used as a phosphate remover in home aquaria.

Hazards of FeO{Iron(II) Oxide}

FeO also have some health hazards and some of the health of the FeO are,

  •  A high level of exposure to Iron (II) oxide may cause illness with flu-like symptoms and siderosis. 
  • Inhalation of fumes or dust of Iron (II) oxide is hazardous as it may cause throat and nasal irritation.

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