Cerium - Ce General Information Discovery Cerium was discovered by J.J. Berzelius and W. Hisinger in 1803 in Vestmanland, Sweden. It was first isolated by Hillebrand and Norton in 1875, in Washington, USA. Appearance Cerium is an iron-grey, lustrous, malleable metal. It oxidises easily at room temperature. Source Cerium is the most abundant of the lanthanides and is found in a number of minerals, chiefly bastnaesite (found in Southern California) and monazite (found in India and Brazil). Metallic cerium can be prepared by two methods. The first is the metallothermic reduction of cerium(III) fluoride with calcium, used to produce high-purity cerium. The second is the electrolysis of molten cerium(III) chloride. Uses Cerium is the major component of mischmetall alloy (just under 50%), which is used extensively in the manufacture of pyrophoric alloys for products such as cigarette lighters. Cerium(Ill) oxide is used as a catalyst in self-cleaning ovens, incorporated into oven walls to prevent the build-up of cooking residues. It is also a promising new petroleum-cracking catalyst. Biological Role Cerium has no known biological role. General Information Cerium tarnishes in air and reacts rapidly with water, especially when hot. It burns when heated. It is attacked by alkali solutions and all acids. The pure metal is likely to ignite when scratched with a knife. Cerium is interesting because of its variable electronic structure. The energy of the inner 4f level is nearly the same as that of the 6s level, and this gives rise to variable occupancy of these two levels and subsequent variable oxidation states.

	Physical Information
	Atomic Number		58
	Relative Atomic Mass (12C=12.000)		140.12
	Melting Point/K		1072
	Boiling Point/K		3716
	Density/kg m-3		6773 (298K)
	Ground State Electron Configuration		[Xe]4f15d16s2
	Electron Affinity(M-M-)/kJ mol-1		-50

	Key Isotopes
	nuclide	136Ce	138Ce	139Ce	140Ce	141Ce
	atomic mass		137.9		139.9
	natural abundance	0.19%	0.25%	0%	88.48%	0%
	half-life	stable	stable	140 days	stable	32.5 days
	nuclide	142Ce	143Ce	144Ce
	atomic mass	141.9
	natural abundance	11.08%	0%	0%
	half-life	stable	33 h	284.9 days

Other Information
Enthalpy of Fusion/kJ mol-1		8.87
Enthalpy of Vaporisation/kJ mol-1		398
Oxidation States
main	Ce+3
others	Ce+4

	Ionisation Energies/kJ mol-1
	M - M+	527.4
	M+ - M2+	1047
	M2+ - M3+	1949
	M3+ - M4+	3547
	M4+ - M5+	6800
	M5+ - M6+	8200
	M6+ - M7+	9700
	M7+ - M8+	11800
	M8+ - M9+	13200
	M9+ - M10+	14700