|Molar mass||70.9374 g/mol|
|Appearance||green crystals or powder|
|Melting point||1,945 °C; 3,533 °F; 2,218 K|
|Solubility in water||insoluble|
|Solubility||soluble in acid|
|Refractive index (nD)||2.16|
|Crystal structure||Halite (cubic), cF8|
|Space group||Fm3m, No. 225|
|Octahedral (Mn2+); octahedral (O2–)|
|Std enthalpy of
|EU Index||Not listed|
|Other anions||Manganese difluoride
|Other cations||Iron(II) oxide|
|Related manganese oxides||Manganese(II,III) oxide
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Manganese(II) oxide (systematically named manganese(2+) oxide(2−)) is an inorganic compound with chemical formula MnO. It forms green crystals and is odorless. Manganese(II) oxide is the simplest ionic manganese oxide. Although it is classified as a very strong base, dissolved manganese(II) oxide is non-corrosive and does not attack the skin.
The oxide anion (O2−) in ionic manganese oxides such as manganese(II) oxide can assimilate a proton by recombination:
- O2− + H+ → HO−
Because of this capture of a proton (H+), manganese(II) oxide has basic character. In aqueous solution, it has a pKb value of ~−38. Oxide's conjugate acid is hydroxide (OH−). A saturated solution has a near neutral pOH, indicating that most oxide ions are associated.
- O2− + H2O 2 HO−
MnO has the NaCl, rock salt structure, where cations and anions are both octahedrally coordinated. The composition of MnO can vary from MnO to MnO1.045.
Below 118 K MnO is antiferromagnetic. MnO has the distinction of being one of the first compounds to have its magnetic structure determined by neutron diffraction in 1951. This study showed that the Mn2+ ions form a face centered cubic magnetic sub-lattice where there are ferromagnetically coupled sheets which are anti-parallel with adjacent sheets.
Manganese(II) oxide undergoes the typical chemical reactions of an ionic manganese oxide. Upon treatment with a standard acid, it converts to a manganese(II) salt and water. Oxidation of manganese(II) oxide gives manganese dioxide.
Preparation and occurrence
MnO can be prepared by the reduction of any higher oxide with hydrogen e.g.:
- MnO2 + H2 → MnO + H2O
- MnO2 + CO → MnO + CO2
MnO can also be prepared by heating MnCO3:
- MnCO3 → MnO + CO2
Together with manganese sulfate, MnO is a component of fertilizer and food additives. Many thousands of tons are consumed annually for this purpose.
- Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X.
- Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_123
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- J.E Greedon, (1994), Magnetic oxides in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
- Neutron Diffraction by Paramagnetic and Antiferromagnetic Substances C. G. Shull, W. A. Strauser, and E. O. Wollan, Phys. Rev. 83, 333 - 345 (1951), doi:10.1103/PhysRev.83.333
- W.H. McCarroll (1994) Oxides- solid sate chemistry, Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0