Cerium
Pronunciation | /ˈ s ɪər i ə m/ ​(SEER-ee-əm)
Appearance | silvery white
Standard atomic weight Ar, std(Ce) | 140.116(1)
Atomic number (Z) | 58
Group | group n/a
Period | period 6
Block | f-block
Element category | Lanthanide
Electron configuration | [Xe] 4f1 5d1 6s2
Electrons per shell | 2, 8, 18, 19, 9, 2
Phase at STP | solid
Melting point | 1068 K ​(795 °C, ​1463 °F)
Boiling point | 3716 K ​(3443 °C, ​6229 °F)
Density (near r.t.) | 6.770 g/cm3
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)
Oxidation states | +1, +2, +3, +4 (a mildly basic oxide)
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
Natural occurrence | primordial
Speed of sound thin rod | 2100 m/s (at 20 °C)
Thermal expansion | γ, poly: 6.3 µm/(m·K) (at r.t.)
Thermal conductivity | 11.3 W/(m·K)
Electrical resistivity | β, poly: 828 nΩ·m (at r.t.)
Magnetic ordering | paramagnetic
Magnetic susceptibility | (β) +2450.0·10−6 cm3/mol (293 K)
Young's modulus | γ form: 33.6 GPa
Shear modulus | γ form: 13.5 GPa
Bulk modulus | γ form: 21.5 GPa
Poisson ratio | γ form: 0.24
Mohs hardness | 2.5
Vickers hardness | 210–470 MPa
Brinell hardness | 186–412 MPa
CAS Number | 7440-45-1
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)