Terbium (atomic symbol: Tb) is a lanthanide series, rare earth element with an atomic number of 65 and an atomic weight of 158.9254. A silvery-gray metal, terbium has a melting point of 2473°F (1356°C) and a boiling point of 5846°F (3230°C). It is malleable, ductile, and so soft it can be cut with a knife.
During the period from 1839-1843, Swedish chemist Carl Gustaf Mosander (1797-1858) attacked one of the most confusing and frustrating problems facing chemists of the time: the composition of the rare earth minerals. In 1839, he discovered that one of those minerals, "erbia," contained at least two new elements (lanthanum and cerium). In 1843, Mosander attacked a second mineral, yttria, and found that it, too, was a complex mixture. This mineral eventually yielded ten new elements. Mosander is given credit for the discovery of one of these--terbium--although his work also contributed to the identification of others in the group. Terbium was isolated in a more pure form by Jean-Charles-Galissard de Marignac (1817-1894) in 1886.
Like the elements erbium, yttrium, and ytterbium, terbium is named for the Swedish town of Ytterby, the place where the rare earth minerals were first found.
The double salt, TbF3ZnS, is used in phosphors in color television sets. When hit with an electron beam, the compound emits a green color. The element is also used as a dopant in calcium and strontium salts used in solid-state devices. Research shows that terbium may also be useful as a stabilizer in hydrogen fuel cells.