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Magnesium oxide facts for kids

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Magnesium oxide
Magnesium oxide.jpg
NaCl polyhedra.png
IUPAC name Magnesium oxide
Other names Magnesia
CAS number 1309-48-4
PubChem 14792
EC number 215-171-9
RTECS number OM3850000
Molecular formula MgO
Molar mass 40.304 g/mol
Appearance White powder
Odor Odorless
Density 3.6 g/cm3
Melting point

2852 °C, 3125 K, 5166 °F

Boiling point

3600 °C, 3873 K, 6512 °F

Solubility Soluble in acid, ammonia
insoluble in alcohol
Band gap 7.8 eV
−10.2·10−6 cm3/mol
Thermal conductivity 45–60 W·m−1·K−1
Refractive index (nD) 1.7355
Dipole moment 6.2 ± 0.6 D
Crystal structure Halite (cubic), cF8
Space group Fm3m, No. 225
Lattice constant a = 4.212Å
Octahedral (Mg2+); octahedral (O2−)
Std enthalpy of
formation ΔfHo298
−601.6 ± 0.3 kJ·mol−1
Standard molar
entropy So298
26.95 ± 0.15 J·mol−1·K−1
Specific heat capacity, C 37.2 J/mol K
ATC code
Main hazards Metal fume fever, Irritant
NFPA 704

NFPA 704.svg

R-phrases R36, R37, R38
Flash point Non-flammable
U.S. Permissible
exposure limit (PEL)
TWA 15 mg/m3 (fume)
Related compounds
Other anions Magnesium sulfide
Other cations Beryllium oxide
Calcium oxide
Strontium oxide
Barium oxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Magnesium oxide, or magnesia, is a white solid mineral, made of one part magnesium and one part oxygen. Its chemical formula is MgO. Magnesium oxide is used by libraries to make books last longer. It is also used as an insulator for some electrical wires, and to help crucibles resist high temperatures. Magnesium oxide is also used to treat heartburn and upset stomachs.

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