Terbium Facts - Tb or Atomic Number 65

Chemical & Physical Properties

Terbium atomic data

Malachy120 / Getty Images

Terbium is a soft, silvery rare earth metal with element symbol Tb and atomic number 65. It isn't found free in nature, but it occurs in many minerals and is used in green phosphors and solid state devices. Get terbium facts and figures. Learn about the properties of this important element:

Terbium Basic Facts

Atomic Number: 65

Symbol: Tb

Atomic Weight: 158.92534

Discovery: Carl Mosander 1843 (Sweden)

Electron Configuration: [Xe] 4f9 6s2

Element Classification: Rare Earth (Lanthanide)

Word Origin: Named after Ytterby, a village in Sweden.

Uses: Terbium oxide is the green phosphor found in color television tubes, trichromatic lighting, and fluorescent lamps. Its phosphorescence also makes it used as a probe in biology Terbium is used to dope calcium tungstate, calcium fluoride, and strontium molybdate to make solid state devices. It is used to stabilize crystals in fuel cells. The element occurs in many alloys. One alloy (Terfenol-D) expands or contracts when exposed to a magnetic field.

Biological Role: Terbium serves no known biological role. Like other lanthanides, the element and its compounds exhibit low to moderate toxicity.

This is a photo of terbium, one of the rare earth elements. Terbium is a soft silvery-white metal.
This is a photo of terbium, one of the rare earth elements. Terbium is a soft silvery-white metal. Tomihahndorf, Free Documentation License

Terbium Physical Data

Density (g/cc): 8.229

Melting Point (K): 1629

Boiling Point (K): 3296

Appearance: soft, ductile, silvery-gray, rare-earth metal

Atomic Radius (pm): 180

Atomic Volume (cc/mol): 19.2

Covalent Radius (pm): 159

Ionic Radius: 84 (+4e) 92.3 (+3e)

Specific Heat (@20°C J/g mol): 0.183

Evaporation Heat (kJ/mol): 389

Pauling Negativity Number: 1.2

First Ionizing Energy (kJ/mol): 569

Oxidation States: 4, 3

Lattice Structure: Hexagonal

Lattice Constant (Å): 3.600

Lattice C/A Ratio: 1.581


  • Emsley, John (2011). Nature's building blocks: An A-Z Guide to the Elements. Oxford University Press. ISBN 978-0-19-960563-7.
  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  • Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.