Magnesium - Mg General Information Discovery Joseph Black recognised magnesium as an element in 1755, but it was first isolated by Sir Humphrey Davy in 1808, and prepared in coherent form by Bussy in 1831. Appearance Magnesium is a silvery-white, lustrous and relatively soft metal, which tarnishes slightly in air. Source Magnesium is the eighth most abundant element in the Earth's crust, but does not occur uncombined. It is found in large deposits in minerals such as magnesite and dolomite. Commercially, it is prepared by electrolysis of fused magnesium chloride derived from brines, wells and sea water. Uses Magnesium is used in photography, flares, pyrotechnics and incendiary bombs. As it is one-third less dense than aluminium, its alloys are useful in aeroplane and missile construction. It improves the mechanical, fabrication and welding characteristics of aluminium when used as an alloying agent. Magnesium hydoxide (milk of magnesia), sulfate (Epsom salts), chloride and citrate are used in medicine. Grignard reagents, which are organic magnesium compounds, are important commercially. Biological Role Magnesium is an essential element in both plant and animal life. It is non-toxic. Chlorophylls are magnesium-centred porphyrins. General Information Great care should be taken in handling magnesium metal, especially in the finely-divided state, as serious fires can occur. Water should not be used on burning magnesium or magnesium fires.

	Physical Information
	Atomic Number		12
	Relative Atomic Mass (12C=12.000)		24.305
	Melting Point/K		922
	Boiling Point/K		1363
	Density/kg m-3		1738 (293K)
	Ground State Electron Configuration		[Ne]3s2
	Electron Affinity(M-M-)/kJ mol-1		+67

	Key Isotopes
	nuclide	24Mg	25Mg	26Mg
	atomic mass	23.985	24.986	25.983
	natural abundance	78.99%	10.00%	11.01%
	half-life	stable	stable	stable

Other Information
Enthalpy of Fusion/kJ mol-1		9.04
Enthalpy of Vaporisation/kJ mol-1		127.6
Oxidation States
Mg+2

	Ionisation Energies/kJ mol-1
	M - M+	737.7
	M+ - M2+	1450.7
	M2+ - M3+	7732.6
	M3+ - M4+	10540
	M4+ - M5+	13630
	M5+ - M6+	17995
	M6+ - M7+	21703
	M7+ - M8+	25656
	M8+ - M9+	31642
	M9+ - M10+	35461