Palladium - Pd General Information Discovery Palladium was discovered by W.H. Wollaston in 1803 in London. Appearance Palladium is a steel-white metal which is lustrous, malleable and ductile. It does not tarnish in air. Source It is found associated with platinum and other metals in deposits in the former USSR, North and South America and Australia. It is also found associated with nickel-copper deposits in South Africa and USA. It is extracted commercially from these latter ores. Uses Finely divided palladium is a good catalyst and is used for hydrogenation and dehydrogenation reactions. White gold is an alloy of gold decolourised by the addition of palladium. It is also used with gold, silver and other metals as a "stiffener" in dental inlays and bridgework. Hydrogen easily diffuses through heated palladium and this provides a way of purifying the gas. Biological Role Palladium has no known biological role, and is non-toxic. General Information Palladium resists corrosion, but reacts with oxidising acids and fused alkalis. At room temperature the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen.

	Physical Information
	Atomic Number		46
	Relative Atomic Mass (12C=12.000)		106.42
	Melting Point/K		1825
	Boiling Point/K		3413
	Density/kg m-3		12020 (293K)
	Ground State Electron Configuration		[Kr]4d10
	Electron Affinity(M-M-)/kJ mol-1		-98.4

	Key Isotopes
	nuclide	102Pd	103Pd	104Pd	105Pd	106Pd
	atomic mass	101.901		103.90	104.90	105.90
	natural abundance	1.02%	0%	11.14%	22.33%	27.33%
	half-life	stable	17 days	stable	stable	stable
	nuclide	108Pd	109Pd	110Pd
	atomic mass	107.90
	natural abundance	26.46%	0%	11.72%
	half-life	stable	13.47 h	stable

Other Information
Enthalpy of Fusion/kJ mol-1		17.2
Enthalpy of Vaporisation/kJ mol-1		361.5
Oxidation States
main	Pd+2
others	Pd0, Pd+4

	Ionisation Energies/kJ mol-1
	M - M+	805
	M+ - M2+	1875
	M2+ - M3+	3177
	M3+ - M4+	4700
	M4+ - M5+	6300
	M5+ - M6+	8700
	M6+ - M7+	10700
	M7+ - M8+	12700
	M8+ - M9+	15000
	M9+ - M10+	17200