Rhodium - Rh General Information Discovery Rhodium was discovered by W.H. Wollaston in 1803 in London. Appearance Rhodium is a lustrous, silvery, hard metal. Source Rhodium occurs native with other platinum metals in river sands in North and South America, and in the copper-nickel sulfide ores of Ontario. Although the quantity occuring here is very small, the large amounts of nickel processed make the extraction of rhodium as a by-product commercially feasible. Uses The major use of rhodium is as a hardener for platinum and palladium, to produce alloys used for electrodes, furnace windings, crucibles and thermocouple elements. It is used as an electrical contact material as it has a low resistance and is highly resistant to corrosion. Plated rhodium is exceptionally hard and is used for optical instruments. It is also used as a catalyst. Biological Role Rhodium has no known biological role, but is a suspected carcinogen. General Information Rhodium is inert to all acids but attacked by fused alkalis. It is stable in air up to 875K.

	Physical Information
	Atomic Number		45
	Relative Atomic Mass (12C=12.000)		102.91
	Melting Point/K		2239
	Boiling Point/K		4000
	Density/kg m-3		12410 (293K)
	Ground State Electron Configuration		[Kr]4d85s1
	Electron Affinity(M-M-)/kJ mol-1		-162

	Key Isotopes
	nuclide	103Rh	105Rh
	atomic mass	102.91
	natural abundance	100%	0%
	half-life	stable	35.88 h

Other Information
Enthalpy of Fusion/kJ mol-1		21.55
Enthalpy of Vaporisation/kJ mol-1		494.3
Oxidation States
main	Rh+3
others	Rh-1, Rh0, Rh+1, Rh+2,
	Rh+4, Rh+5, Rh+6

	Ionisation Energies/kJ mol-1
	M - M+	720
	M+ - M2+	1744
	M2+ - M3+	2997
	M3+ - M4+	4400
	M4+ - M5+	6500
	M5+ - M6+	8200
	M6+ - M7+	10100
	M7+ - M8+	12200
	M8+ - M9+	14200
	M9+ - M10+	22000