Terbium (Tb)

Terfenol-D, an alloy of terbium, dysprosium and iron, changes length by about 0.2% in a magnetic field — an enormous magnetostriction that lets it act as a solid-state actuator or turn any flat surface into a loudspeaker. Terbium is one of the four elements named after Ytterby in Sweden, along with yttrium, erbium and ytterbium, all from the same small quarry. Adding a few percent of terbium to a neodymium magnet raises the temperature it can work at, which is why electric car motors consume more of it than anything else.

Properties

Atomic number

65

Symbol

Tb

Standard atomic weight

158.93 u

Category

Lanthanide

Period

6

Block

f-block

Electron configuration

[Xe] 6s² 4f⁹

Electrons per shell

2, 8, 18, 27, 8, 2

Melting point

1,629 K — 1355.8 °C — 2472.5 °F

Boiling point

3,503 K — 3229.8 °C — 5845.7 °F

Density

8.23 g/cm³

Oxidation states

+3

Discovered

1843 by Carl Gustaf Mosander

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁹

Noble gas shorthand

[Xe] 6s² 4f⁹

Shells

K: 2 · L: 8 · M: 18 · N: 27 · O: 8 · P: 2

What it is used for

• Green phosphors in fluorescent lamps and LED lighting
• Terfenol-D magnetostrictive actuators and sonar transducers
• Raising the working temperature of neodymium magnets
• X-ray intensifying screens

No Pauling electronegativity is listed in the standard tables for terbium.

Neighbours in the table