Manganese(II) oxide

Manganese(II) oxide is an inorganic compound with chemical formula MnO.^[2] It forms green crystals. The compound is produced on a large scale as a component of fertilizers and food additives.

Manganese(II) oxide

Manganese(II) oxide
Names
IUPAC name Manganese(II) oxide
Other names Manganous oxide Manganosite manganese monoxide oxomanganese
Identifiers
CAS Number	1344-43-0 Y
3D model (JSmol)	Interactive image
ChemSpider	14234
ECHA InfoCard	100.014.269
EC Number	215-695-8
PubChem CID	14940
RTECS number	OP0900000
UNII	64J2OA7MH3 Y
CompTox Dashboard (EPA)	DTXSID5042110
InChI InChI=1S/Mn.O Key: VASIZKWUTCETSD-UHFFFAOYSA-N
SMILES [Mn+2].[O-2]
Properties
Chemical formula	MnO
Molar mass	70.9374 g/mol
Appearance	green crystals or powder
Density	5.43 g/cm3
Melting point	1,945 °C (3,533 °F; 2,218 K)
Solubility in water	insoluble
Solubility	soluble in acid
Magnetic susceptibility (χ)	+4850.0·10−6 cm3/mol
Refractive index (nD)	2.16
Structure
Crystal structure	Halite (cubic), cF8
Space group	Fm3m, No. 225
Coordination geometry	Octahedral (Mn2+); octahedral (O2−)
Thermochemistry
Std molar entropy (S⦵298)	60 J·mol−1·K−1[1]
Std enthalpy of formation (ΔfH⦵298)	−385 kJ·mol−1[1]
Hazards
NFPA 704 (fire diamond)	1 0 0
Flash point	Non-flammable
Related compounds
Other anions	Manganese(II) fluoride Manganese(II) sulfide Manganese(II) selenide Manganese(II) telluride
Other cations	Iron(II) oxide
Related manganese oxides	Manganese(II,III) oxide Manganese(III) oxide Manganese dioxide Manganese heptoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Structure, stoichiometry, reactivity

Like many metal monoxides, MnO adopts the rock salt structure, where cations and anions are both octahedrally coordinated. Also like many metal oxides, manganese(II) oxide is often nonstoichiometric: its composition can vary from MnO to MnO_1.045.^[3]

Below 118 K, MnO is antiferromagnetic.^[3] MnO has the distinction of being one of the first compounds^[4] to have its magnetic structure determined by neutron diffraction, the report appearing in 1951.^[5] This study showed that the Mn²⁺ ions form a face centered cubic magnetic sub-lattice where there are ferromagnetically coupled sheets that are anti-parallel with adjacent sheets.

Manganese(II) oxide undergoes the chemical reactions typical of an ionic oxide. Upon treatment with acids, it converts to the corresponding manganese(II) salt.^[3] Oxidation of manganese(II) oxide gives manganese(III) oxide.

Preparation and occurrence

MnO occurs in nature as the rare mineral manganosite.
It is prepared commercially by reduction of MnO₂ with hydrogen, carbon monoxide or methane, e.g.:^[2]

MnO₂ + H₂ → MnO + H₂O

MnO₂ + CO → MnO + CO₂

Upon heating to 450 °C, manganese(II) nitrate gives a mixture of oxides, denoted MnO_2−x, which can be reduced to the monoxide with hydrogen at ≥750 °C.^[6] MnO is particularly stable and resists further reduction.^[7] MnO can also be prepared by heating the carbonate:^[8]

MnCO₃ → MnO + CO₂

This calcining process is conducted anaerobically, lest Mn₂O₃ form.

An alternative route, most interest for demonstration purposes, is the "oxalate method". Also applicable to the synthesis of ferrous oxide and stannous oxide, it entails heating in an oxygen-free atmosphere (often CO₂), hydrated manganese(II) oxalate:^[9]

MnC₂O₄·2H₂O → MnO + CO₂ + CO + 2 H₂O

Applications

Together with manganese sulfate, MnO is a component of fertilizers and food additives. Many thousands of tons are consumed annually for this purpose. Other uses include: a catalyst in the manufacture of allyl alcohol, ceramics, paints, colored glass, bleaching tallow and textile printing.^[2]