Cerium

Cerium, ₅₈Ce

Cerium
Pronunciation	/ˈsɪəriəm/ ​(SEER-ee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Ce)
	140.116±0.001[1] 140.12±0.01 (abridged)[2]
Cerium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ Ce ↓ Th lanthanum ← cerium → praseodymium
Atomic number (Z)	58
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f1 5d1 6s2[3]
Electrons per shell	2, 8, 18, 19, 9, 2
Physical properties
Phase at STP	solid
Melting point	1068 K ​(795 °C, ​1463 °F)
Boiling point	3716 K ​(3443 °C, ​6229 °F)
Density (at 20° C)	β-Ce: 6.689 g/cm3 γ-Ce: 6.769 g/cm3 [4]
when liquid (at m.p.)	6.55 g/cm3
Heat of fusion	5.46 kJ/mol
Heat of vaporization	398 kJ/mol
Molar heat capacity	26.94 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1992 2194 2442 2754 3159 3705
Atomic properties
Oxidation states	common: +3, +4 +1,? +2[5]
Electronegativity	Pauling scale: 1.12
Ionization energies	1st: 534.4 kJ/mol 2nd: 1050 kJ/mol 3rd: 1949 kJ/mol (more)
Atomic radius	empirical: 181.8 pm
Covalent radius	204±9 pm
Spectral lines of cerium
Other properties
Natural occurrence	primordial
Crystal structure	β-Ce: ​double hexagonal close-packed (dhcp) (hP4)
Lattice constants	a = 0.36811 nm c = 1.1857 nm (at 20 °C)[4]
Crystal structure	γ-Ce: ​face-centered cubic (fcc) (cF4)
Lattice constant	a = 0.51612 nm (at 20 °C)[4]
Thermal expansion	β-Ce: 6.1×10−6/K γ-Ce: 6.1×10−6/K (at 20 °C)[4]
Thermal conductivity	11.3 W/(m⋅K)
Electrical resistivity	β-Ce, poly: 828 nΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic[6]
Molar magnetic susceptibility	β-Ce: +2450.0×10−6 cm3/mol (293 K)[7]
Young's modulus	γ-Ce: 33.6 GPa
Shear modulus	γ-Ce: 13.5 GPa
Bulk modulus	γ-Ce: 21.5 GPa
Speed of sound thin rod	2100 m/s (at 20 °C)
Poisson ratio	γ-Ce: 0.24
Mohs hardness	2.5
Vickers hardness	210–470 MPa
Brinell hardness	186–412 MPa
CAS Number	7440-45-1
History
Naming	after dwarf planet Ceres, itself named after Roman deity of agriculture Ceres
Discovery	Martin Heinrich Klaproth, Jöns Jakob Berzelius, Wilhelm Hisinger (1803)
First isolation	Carl Gustaf Mosander (1838)
Isotopes of cerium v e
Main isotopes[8] Decay abun­dance half-life (t1/2) mode pro­duct 134Ce synth 3.16 d ε 134La 136Ce 0.186% stable 138Ce 0.251% stable 139Ce synth 137.640 d ε 139La 140Ce 88.4% stable 141Ce synth 32.501 d β− 141Pr 142Ce 11.1% stable 143Ce synth 33.039 h β− 143Pr 144Ce synth 284.893 d β− 144Pr
Category: Cerium view talk edit | references

Cerium is a chemical element; it has symbol Ce and atomic number 58. It is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is considered one of the rare-earth elements. Cerium has no known biological role in humans but is not particularly toxic, except with intense or continued exposure.

Despite always occurring in combination with the other rare-earth elements in minerals such as those of the monazite and bastnäsite groups, cerium is easy to extract from its ores, as it can be distinguished among the lanthanides by its unique ability to be oxidized to the +4 state in aqueous solution. It is the most common of the lanthanides, followed by neodymium, lanthanum, and praseodymium. Its estimated abundance in the Earth's crust is 68 ppm.

Cerium was the first of the lanthanides to be discovered, in Bastnäs, Sweden. It was discovered by Jöns Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year. In 1839 Carl Gustaf Mosander became the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, cerium(IV) oxide is used to polish glass and is an important part of catalytic converters. Cerium metal is used in ferrocerium lighters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources.