terbium

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terbium (symbol Tb) Silver-grey, metallic element of the lanthanide series (rare-earth metals). It is found in such minerals as monazite, gladolinite, and apatite. The soft element is used in semiconductors; sodium terbium borate is used in lasers. It was discovered in 1843 by the Swedish chemist Carl Mosander. Properties: at.no. 65; r.a.m. 158.9254; r.d. 8.234; m.p. 1360°C (2480°F); b.p. 3041°C (5506°F). Single isotope Tb159.

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