Terbium
Pronunciation | /ˈ t ɜːr b i ə m/ ​(TUR-bee-əm)
Appearance | silvery white
Standard atomic weight Ar, std(Tb) | 158.925354(8)
Atomic number (Z) | 65
Group | group n/a
Period | period 6
Block | f-block
Element category | Lanthanide
Electron configuration | [Xe] 4f9 6s2
Electrons per shell | 2, 8, 18, 27, 8, 2
Phase at STP | solid
Melting point | 1629 K ​(1356 °C, ​2473 °F)
Boiling point | 3396 K ​(3123 °C, ​5653 °F)
Density (near r.t.) | 8.23 g/cm3
when liquid (at m.p.) | 7.65 g/cm3
Heat of fusion | 10.15 kJ/mol
Heat of vaporization | 391 kJ/mol
Molar heat capacity | 28.91 J/(mol·K)
Oxidation states | 0, +1, +2, +3, +4 (a weakly basic oxide)
Electronegativity | Pauling scale: 1.2 (?)
Ionization energies | 1st: 565.8 kJ/mol 2nd: 1110 kJ/mol 3rd: 2114 kJ/mol
Atomic radius | empirical: 177 pm
Covalent radius | 194±5 pm
Natural occurrence | primordial
Speed of sound thin rod | 2620 m/s (at 20 °C)
Thermal expansion | at r.t. α, poly: 10.3 µm/(m·K)
Thermal conductivity | 11.1 W/(m·K)
Electrical resistivity | α, poly: 1.150 µΩ·m (at r.t.)
Magnetic ordering | paramagnetic at 300 K
Magnetic susceptibility | +146,000·10−6 cm3/mol (273 K)
Young's modulus | α form: 55.7 GPa
Shear modulus | α form: 22.1 GPa
Bulk modulus | α form: 38.7 GPa
Poisson ratio | α form: 0.261
Vickers hardness | 450–865 MPa
Brinell hardness | 675–1200 MPa
CAS Number | 7440-27-9
Naming | after Ytterby (Sweden), where it was mined
Discovery and first isolation | Carl Gustaf Mosander (1843)