Arsenic - As General Information Discovery Arsenic was discovered in 1250 A.D. by A. Magnus, and first prepared by Schroeder in 1649. Appearance Arsenic is a steel grey, brittle, crystalline metalloid. Source The most common arsenic-containing mineral is mispickel, and others include realgar and orpiment. Arsenic can also be found in the native state. It can be obtained from mispickel by heating, which causes the arsenic to sublime and leaves the iron(II) sulfide. Uses Arsenic is used in bronzing, pyrotechnics and for hardening shot. It is increasingly being used as a doping agent in solid state devices. Biological Role Arsenic may be an essential element, but it is certainly toxic in small doses and also a suspected carcinogen. Calcium and lead arsenic compounds are used as poisons for vermin. General Information Arsenic has several allotropes. The most common is grey arsenic, which tarnishes and burns in oxygen. It resists attack by acids, alkalis and water but is attacked by hot acids and molten sodium hydroxide. When heated, it sublimes.

	Physical Information
	Atomic Number		33
	Relative Atomic Mass (12C=12.000)		74.923
	Melting Point/K		1090 (alpha form under pressure)
	Boiling Point/K		889 (sublimes)
	Density/kg m-3		5780 (293K) (alpha form)
	Ground State Electron Configuration		[Ar]3d104s24p3
	Electron Affinity(M-M-)/kJ mol-1		-77

	Key Isotopes
	nuclide	73As	74As	75As	76As
	atomic mass	72.924	73.924	74.922	75.922
	natural abundance	0%	0%	100%	0%
	half-life	80.3 days	17.9 days	stable	26.5 h

Other Information
Enthalpy of Fusion/kJ mol-1		27.7
Enthalpy of Vaporisation/kJ mol-1		31.9
Oxidation States
main	As+3, As+5
others	As-3
Covalent Bonds /kJ mol-1
As - H	245
As -C	200
As - O	477
As - F	464
As - Cl	293
As - As	348

	Ionisation Energies/kJ mol-1
	M - M+	947
	M+ - M2+	1798
	M2+ - M3+	2735
	M3+ - M4+	4837
	M4+ - M5+	6042
	M5+ - M6+	12305
	M6+ - M7+	15400
	M7+ - M8+	18900
	M8+ - M9+	22600
	M9+ - M10+	26400