Cerium
Pronunciation/ˈsɪəriəm/ (SEER-ee-əm)
Appearancesilvery white
Standard atomic weight Ar, std(Ce)140.116(1)
Atomic number (Z)58
Groupgroup n/a
Periodperiod 6
Blockf-block
Element category  Lanthanide
Electron configuration[Xe] 4f1 5d1 6s2
Electrons per shell
2, 8, 18, 19, 9, 2
Phase at STPsolid
Melting point1068 K ​(795 °C, ​1463 °F)
Boiling point3716 K ​(3443 °C, ​6229 °F)
Density (near r.t.)6.770 g/cm3
when liquid (at m.p.)6.55 g/cm3
Heat of fusion5.46 kJ/mol
Heat of vaporization398 kJ/mol
Molar heat capacity26.94 J/(mol·K)
Oxidation states+1, +2, +3, +4 (a mildly basic oxide)
ElectronegativityPauling scale: 1.12
Ionization energies
  • 1st: 534.4 kJ/mol
  • 2nd: 1050 kJ/mol
  • 3rd: 1949 kJ/mol
  • (more)
Atomic radiusempirical: 181.8 pm
Covalent radius204±9 pm
Natural occurrenceprimordial
Speed of sound thin rod2100 m/s (at 20 °C)
Thermal expansionγ, poly: 6.3 µm/(m·K) (at r.t.)
Thermal conductivity11.3 W/(m·K)
Electrical resistivityβ, poly: 828 nΩ·m (at r.t.)
Magnetic orderingparamagnetic
Magnetic susceptibility(β) +2450.0·10−6 cm3/mol (293 K)
Young's modulusγ form: 33.6 GPa
Shear modulusγ form: 13.5 GPa
Bulk modulusγ form: 21.5 GPa
Poisson ratioγ form: 0.24
Mohs hardness2.5
Vickers hardness210–470 MPa
Brinell hardness186–412 MPa
CAS Number7440-45-1
Namingafter dwarf planet Ceres, itself named after Roman deity of agriculture Ceres
DiscoveryMartin Heinrich Klaproth, Jöns Jakob Berzelius, Wilhelm Hisinger (1803)
First isolationCarl Gustaf Mosander (1838)