Tantalum - Ta General Information Discovery Tantalum was discovered by A.G. Ekeberg in 1802 in Uppsala, Sweden, but many chemists thought that tantalum and niobium were identical elements until Rose (in 1844) and Marignac (in 1866) showed that niobic and tantalic acids were different. Appearance Tantalum is a shiny, grey metal which is soft when pure. Source Tantalum occurs principally in the mineral columbite-tantalite, found in many places including Australia, Canada and Africa. Separation of tantalum from niobium requires several complicated steps. It is obtained commercially as a by-product of tin extraction. Uses Tantalum causes no immune response in mammals, so has found wide use in the making of surgical appliances. It can replace bone, for example in skull plates; as foil or wire it connects torn nerves; as woven gauze it binds abdominal muscle. Tantalum has also been used to make a variety of alloys. Biological Role Tantalum has no known biological role, and is non-toxic. General Information Tantalum is very corrosion resistant due to the formation of an oxide film, but is attacked by hydrogen fluoride and fused alkalis. It has a melting point exceeded only by tungsten and rhenium.

	Physical Information
	Atomic Number		73
	Relative Atomic Mass (12C=12.000)		180.95
	Melting Point/K		3269
	Boiling Point/K		5698
	Density/kg m-3		16654 (293K)
	Ground State Electron Configuration		[Xe]4f145d36s2
	Electron Affinity(M-M-)/kJ mol-1		-14

	Key Isotopes
	nuclide	180Ta	181Ta	182Ta
	atomic mass	179.9	180.9
	natural abundance	0.012%	99.99%	0%
	half-life	1x1012 yrs	stable	115.1 days

Other Information
Enthalpy of Fusion/kJ mol-1		31.4
Enthalpy of Vaporisation/kJ mol-1		758.2
Oxidation States
main	Ta+5
others	Ta-3, Ta-1, Ta+1, Ta+2,
	Ta+3, Ta+6

	Ionisation Energies/kJ mol-1
	M - M+	761
	M+ - M2+	1500
	M2+ - M3+	2100
	M3+ - M4+	3200
	M4+ - M5+	4300
	M5+ - M6+
	M6+ - M7+
	M7+ - M8+
	M8+ - M9+
	M9+ - M10+