Magnesium oxide

Magnesium oxide
Names
	IUPAC name Magnesium oxide
	Other names Magnesia; Periclase
Properties
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
Solubility	Soluble in acid, ammonia ; insoluble in alcohol
Band gap	7.8 eV
Magnetic susceptibility (χ)	−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
Structure
Crystal structure	Halite (cubic), cF8
Space group	Fm3m, No. 225
Lattice constant	a = 4.212Å
Coordination; geometry	Octahedral (Mg2+); octahedral (O2−)
Thermochemistry
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
Pharmacology
ATC code
Hazards
Main hazards	Metal fume fever, Irritant
NFPA 704	0 1 0
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

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 made to treat heartburn and upset stomachs.^{[verification needed]}