CERIUM

TRANSITION ELEMENT: LANTHANIDE

Atomic number:	58
Group numbers:	3
Period:	6
Electronic configuration:	[Xe] 4f² 6s²
Formal oxidation number:	+3 +4
Electronegativities:	1.12
Atomic radius / pm:	182.5
Relative atomic mass:	140.116(1)

Cerium was discovered by Jöns Jakob Berzelius and Wilhelm Hisinger (SE) in 1803 and independently by Martin Heinrich Klaproth (DE). Named after the asteroid Ceres discovered two years before the element. It is a malleable, ductile, iron-grey metal that tarnishes in air and reacts easily with water. Cerium dissolves in acids and ignites when heated. Metal ignites and burns readily. Strong reductant. Cerium is most abundant rare earth metal. Found in many minerals like monazite sand [Ce(PO4)]. Its oxides are used in the optics and glass-making industries. Its salts are used in the photography and textile industry. Cerium is also used in high-intensity carbon lamps and as alloying agents in special metals. The price of 99.8 % pure cerium ingot is 256.20 € for 250 g.

PHYSICAL PROPERTIES
Density / g dm^-3:	8240	(alpha, 298 K)
	6749	(beta, 298 K)
	6773	(gamma, 298 K)
Molar volume / cm³mol^-1:	17.00	(alpha, 298 K)
	20.76	(beta, 298 K)
	20.69	(gamma, 298 K)
Electrical resistivity / µΩcm:	75	(20 °C)

THERMAL PROPERTIES
Thermal conductivity / W m^-1K^-1:	11.4
Melting point / °C:	798
Boiling point / °C:	3443
Heat of fusion / kJ mol^-1:	8.87
Heat of vaporization / kJ mol^-1:	398
Heat of atomization / kJ mol^-1:	423.4

IONIZATION ENERGIES
First ionization energy / kJ mol^-1:	534.41
Second ionization energy / kJ mol^-1:	1046.87
Third ionization energy / kJ mol^-1:	1948.82

ABUNDANCE OF ELEMENT
in the atmosphere / ppm:	-
in the Earth's crust / ppm:	33
in the oceans / ppm:	0.0004

CRYSTALLOGRAPHIC DATA
Crystal structure:	face-centered cubic
Unit-cell dimensions / pm:	a=485
Space group:	Fm3m

ISOTOPES
Isotope	Relative atomic mass	Mass percent (%)
¹³⁶Ce	135.90714(5)	0.19(1)
¹³⁷Ce	136.90778(5)	*
¹³⁸Ce	137.90599(1)	0.25(1)
¹³⁹Ce	138.906647(8)	*
¹⁴⁰Ce	139.905434(3)	88.48(10)
¹⁴¹Ce	140.908271(3)	*
¹⁴²Ce	141.909240(4)	11.08(10)

REDUCTION POTENTIALS
Balanced half-reaction	E^o / V
Ce³⁺ + 3e^- → Ce(s)	- 2.48
Ce(OH)₂²⁺ + 2H⁺ + e^- → Ce³⁺ + 2H₂O	+1.73
Ce(OH)³⁺ + H⁺ + e^- → Ce³⁺ + H₂O	+1.71
Ce(ClO₄)₆^2- + e^- → Ce³⁺ + 6ClO₄^-	+1.70	(1 mol dm^-3 HClO₄)
Ce(NO₃)₆^2- + e^- → Ce³⁺ + 6NO₃^-	+1.61	(1 mol dm^-3 HNO₃)
Ce(SO₄)₃^2- + e^- → Ce³⁺ + 3SO₄^2-	+1.44	(1 mol dm^-3 H₂SO₄)