Chemical element, symbol Tb and atomic number 65 / From Wikipedia, the free encyclopedia

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Terbium is a chemical element; it has symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.

Quick facts: Terbium, Pronunciation, Appearance, Standard ...
Terbium, 65Tb
Pronunciation/ˈtɜːrbiəm/ (TUR-bee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Tb)
  • 158.925354±0.000007
  • 158.93±0.01 (abridged)[1]
Terbium in the periodic table


Atomic number (Z)65
Groupf-block groups (no number)
Periodperiod 6
Block  f-block
Electron configuration[Xe] 4f9 6s2
Electrons per shell2, 8, 18, 27, 8, 2
Physical properties
Phase at STPsolid
Melting point1629 K (1356 °C, 2473 °F)
Boiling point3396 K (3123 °C, 5653 °F)
Density (near r.t.)8.23 g/cm3
when liquid (at m.p.)7.65 g/cm3
Heat of fusion10.15 kJ/mol
Heat of vaporization391 kJ/mol
Molar heat capacity28.91 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1789 1979 (2201) (2505) (2913) (3491)
Atomic properties
Oxidation states0,[2] +1,[3] +2, +3, +4 (a weakly basic oxide)
ElectronegativityPauling scale: 1.2 (?)
Ionization energies
  • 1st: 565.8 kJ/mol
  • 2nd: 1110 kJ/mol
  • 3rd: 2114 kJ/mol
Atomic radiusempirical: 177 pm
Covalent radius194±5 pm
Color lines in a spectral range
Spectral lines of terbium
Other properties
Natural occurrenceprimordial
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for terbium
Speed of sound thin rod2620 m/s (at 20 °C)
Thermal expansionat r.t. α, poly: 10.3 µm/(m⋅K)
Thermal conductivity11.1 W/(m⋅K)
Electrical resistivityα, poly: 1.150 µΩ⋅m (at r.t.)
Magnetic orderingparamagnetic at 300 K
Molar magnetic susceptibility+146000×10−6 cm3/mol (273 K)[4]
Young's modulusα form: 55.7 GPa
Shear modulusα form: 22.1 GPa
Bulk modulusα form: 38.7 GPa
Poisson ratioα form: 0.261
Vickers hardness450–865 MPa
Brinell hardness675–1200 MPa
CAS Number7440-27-9
Namingafter Ytterby (Sweden), where it was mined
Discovery and first isolationCarl Gustaf Mosander (1843)
Isotopes of terbium
Main isotopes[5] Decay
abun­dance half-life (t1/2) mode pro­duct
157Tb synth 71 y ε 157Gd
158Tb synth 180 y ε 158Gd
β 158Dy
159Tb 100% stable
Symbol_category_class.svg Category: Terbium
| references

Swedish chemist Carl Gustaf Mosander discovered terbium as a chemical element in 1843. He detected it as an impurity in yttrium oxide, Y2O3. Yttrium and terbium, as well as erbium and ytterbium, are named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.

Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate in solid-state devices, and as a crystal stabilizer of fuel cells that operate at elevated temperatures. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and in sensors.

Most of the world's terbium supply is used in green phosphors. Terbium oxide is used in fluorescent lamps and television and monitor cathode-ray tubes (CRTs). Terbium green phosphors are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide trichromatic lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.

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