Chlorine - Cl General Information Discovery Chlorine was discovered in 1774 by C.W. Scheele in Uppsala, Sweden. He thought it contained oxygen and it was Davy who recognised it as an element and named it chlorine in 1810. Appearance Chlorine is a greenish-yellow, dense gas with a sharp smell. Source Chlorine is not found free in nature, but combined chiefly with sodium as sodium chloride in common salt and the minerals carnallite and sylvite. Chlorine is produced commercially by the electrolysis of sodium chloride. Uses Chlorine is widely used in many different areas. It is used in the production of safe drinking water and many consumer products such as paper, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, foodstuffs, solvents, paints and plastics. It is also used to produce chlorates, chloroform, carbon tetrachloride and bromine. A further substantial use for this element is in organic chemistry, both as an oxidising agent and in substitution reactions. Biological Role The chloride ion is essential to life. Chlorine gas is a respiratory irritant, which can be fatal after a few deep breaths. It was used as a war gas in 1915. Chlorine liquid corrodes the skin.

	Physical Information
	Atomic Number		17
	Relative Atomic Mass (12C=12.000)		35.453
	Melting Point/K		172
	Boiling Point/K		239
	Density/kg m-3		3.214 (273K)
	Ground State Electron Configuration		[Ne]3s23p5
	Electron Affinity(M-M-)/kJ mol-1		-348

	Key Isotopes
	nuclide	35Cl	36Cl	37Cl
	atomic mass	34.969	35.980	36.966
	natural abundance	75.77%	0%	24.23%
	half-life	stable	3.1x105 yrs	stable

Other Information
Enthalpy of Fusion/kJ mol-1		6.41
Enthalpy of Vaporisation/kJ mol-1		20.403
Oxidation States
main	Cl-1, Cl+7
others	Cl+1, Cl+3, Cl+4, Cl+5, Cl+6
Covalent Bonds /kJ mol-1
Cl - O	206
Cl - Cl	242
Cl - F	257
Cl - H	431

	Ionisation Energies/kJ mol-1
	M - M+	1251.1
	M+ - M2+	2297
	M2+ - M3+	3826
	M3+ - M4+	5158
	M4+ - M5+	6540
	M5+ - M6+	9362
	M6+ - M7+	11020
	M7+ - M8+	33610
	M8+ - M9+	38600
	M9+ - M10+	43960