Discovery of terbium

Terbium was discovered in 1843 by the Swedish chemist Carl Gustaf Mosander in Stockholm. He found that the mineral yttria, which had itself been identified in the Ytterby quarry, contained two further new substances, which he named erbia and terbia. Terbium is named after Ytterby, the village near Stockholm that gave names to four elements. The confusion between erbium and terbium persisted for decades, since their names were later swapped. Terbium is a silvery rare earth metal that is soft enough to be cut with a knife. Its compounds give off a bright green light under ultraviolet or electron excitation, which made terbium important for the green phosphors in colour televisions and fluorescent lamps, and it is used in some magnets, sensors and sonar systems.

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