Terbium

Symbol: Tb
Date of discovery: 1843
Name origin: Ytterby, Sweden
Appearance: silvery white
Discoverer: Carl Gustaf Musander
Obtained from: cerite, gadolinite, monazite

Melting point: 1360 K
Boiling point: 3230 K
Density[kg/m³]: 8.23
Molar volume: 19.30 × 10^-6 m³/mol
Protons/Electrons: 65
Neutrons: 94
Shell structure: 2,8,18,27,8,2
Electron configuration: [Xe]4f96s2
Oxidation state: 3,4
Crystal structure: hexagonal

Terbium is a silvery-white, rare earth metal found in cerite, gadolinite, and monazite. This element was discovered by Swedish chemist Gustav Mosander, who also discovered lanthanum and erbium. Soft enough to be cut with a knife, terbium melts at 1356°C. Until the recent advent of ion exchange techniques, it had never been isolated in pure form. Sodium terbium borate is used as a laser material and emits coherent light at 0.546 μm. In fuel cells, terbium is often combined with zirconium oxide to stabilize crystals at elevated temperatures.