thulium[t̸ho̵̅o̅′lē əm, t̸hyo̵̅o̅′-]
a bright, silvery chemical element, one of the rare-earth elements: symbol, Tm; at. no., 69
Origin of thuliumModL: so named (1886) by L. de Boisbaudran (see gadolinium) ; from thulia (from which it was isolated by Cleve in 1879) + -ium
A bright, soft, silvery rare-earth metal obtained commercially from monazite, having an x-ray emitting isotope that is used in small portable medical x-ray units. Atomic number 69; atomic weight 168.934; melting point 1,545°C; boiling point 1,950°C; specific gravity 9.321 (at 25°C); valence 2, 3. See Periodic Table.
Origin of thuliumAfter Thule1.
- A metallic chemical element (symbol Tm) with an atomic number of 69.