Science, Tech, Math › Science Terbium Facts - Tb or Atomic Number 65 Chemical & Physical Properties Share Flipboard Email Print Malachy120 / Getty Images Science Chemistry Periodic Table Basics Chemical Laws Molecules Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated December 07, 2019 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. 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 Sources 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.