Atomic number ..... 65
Atomic mass..... 158.92534 g.mol -1
Density ..... 8.3 g.cm-3 at 20°C
Melting point.....1360 °C
Boiling point .... 3041 °C
Discovered .... Carl Mosander in 1843
Terbium is a soft, malleable, ductile, silver-gray metal member of the lanthanide group of the periodic table . It is reasonably stable in air, but it is slowly oxidised and it reacts with cold water.
Terbium is rare and expensive, so it has few commercial uses. Some minor uses are in lasers, semiconductor devices, and phosphorous in colour television tubes. It is also used in solid-state devices, as stabilizer of fuel cells which operate at high temperature.
Terbium is one of the rarer rare-earth elements, although is twice as common in the Earth's crust as silver . It is never found in nature as free element, but is is contained in many minerals. The most important ore are monazite, bastnasite and cerite. The main mining areas are China, USA, India, Sri Lanka, Brazil and Australia and reserves fo terbium are estimated to be around 300.000 tonnes. World production is 10 tonnes a year.
Terbium has no bilogical role, it may be mildly toxic by ingestion. Terbium powder and compound are very irritating if they come into contact with the skin and the eyes. Its toxicity has not been investigated in detail.
Terbium poses no environmental threat to plants or animals.