Magnesium oxide
Chemical compound naturally occurring as periclase / From Wikipedia, the free encyclopedia
Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture.
Quick Facts Names, Identifiers ...
Names | |
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IUPAC name
Magnesium oxide | |
Other names
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Identifiers | |
3D model (JSmol) |
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ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.013.793 |
EC Number |
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E number | E530 (acidity regulators, ...) |
KEGG | |
PubChem CID |
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RTECS number |
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UNII | |
CompTox Dashboard (EPA) |
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Properties | |
MgO | |
Molar mass | 40.304 g/mol[1] |
Appearance | White powder |
Odor | Odorless |
Density | 3.6 g/cm3[1] |
Melting point | 2,852 °C (5,166 °F; 3,125 K)[1] |
Boiling point | 3,600 °C (6,510 °F; 3,870 K)[1] |
Solubility | Soluble in acid, ammonia insoluble in alcohol |
Electrical resistivity | Dielectric[lower-alpha 1] |
Band gap | 7.8 eV[5] |
−10.2·10−6 cm3/mol[6] | |
Thermal conductivity | 45–60 W·m−1·K−1[7] |
Refractive index (nD) |
1.7355 |
6.2 ± 0.6 D | |
Structure | |
Halite (cubic), cF8 | |
Fm3m, No. 225 | |
a = 4.212Å | |
Octahedral (Mg2+); octahedral (O2−) | |
Thermochemistry | |
Heat capacity (C) |
37.2 J/mol K[8] |
Std molar entropy (S⦵298) |
26.95 ± 0.15 J·mol−1·K−1[9] |
Std enthalpy of formation (ΔfH⦵298) |
−601.6 ± 0.3 kJ·mol−1[9] |
Gibbs free energy (ΔfG⦵) |
-569.3 kJ/mol[8] |
Pharmacology | |
A02AA02 (WHO) A06AD02 (WHO), A12CC10 (WHO) | |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards |
Metal fume fever, Irritant |
GHS labelling: | |
Warning | |
H315, H319, H335 | |
P261, P264, P271, P273, P280, P302+P352, P304+P340, P305+P351+P338, P312, P333+P313, P337+P313, P362, P363, P391, P403+P233, P405 | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
NIOSH (US health exposure limits): | |
PEL (Permissible) |
TWA 15 mg/m3 (fume)[10] |
REL (Recommended) |
None designated[10] |
IDLH (Immediate danger) |
750 mg/m3 (fume)[10] |
Safety data sheet (SDS) | ICSC 0504 |
Related compounds | |
Other anions |
Magnesium sulfide Magnesium selenide |
Other cations |
Beryllium oxide Calcium oxide Strontium oxide Barium oxide |
Related compounds |
Magnesium hydroxide Magnesium nitride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from magnesia nigra, a black mineral containing what is now known as manganese.