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n. Symbol Tm
A bright, soft, silvery, metallic element of the lanthanide series obtained commercially from the mineral monazite, having an x-ray emitting isotope that is used in 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.
(Elements & Compounds) a malleable ductile silvery-grey element occurring principally in monazite. The radioisotope thulium-170 is used as an electron source in portable X-ray units. Symbol: Tm; atomic no: 69; atomic wt: 168.93421; valency: 3; relative density: 9.321; melting pt: 1545°C; boiling pt: 1950°C
[C19: New Latin, from Thule + -ium]
thu•li•um(ˈθu li əm)
a rare-earth metallic element found in gadolinite and other uncommon minerals. Symbol: Tm; at. wt.: 168.934; at. no.: 69; sp. gr.: 9.32.
Symbol Tm A soft, easily shaped, silver-gray metallic element of the lanthanide series. An artificial radioactive isotope of thulium is used as a radiation source in small, portable x-ray machines. Atomic number 69. See Periodic Table.
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|Noun||1.||thulium - a soft silvery metallic element of the rare earth group; isotope 170 emits X-rays and is used in small portable X-ray machines; it occurs in monazite and apatite and xenotime|
metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
apatite - a common complex mineral consisting of calcium fluoride phosphate or calcium chloride phosphate; a source of phosphorus
monazite - a reddish-brown mineral containing rare earth metals; an important source of thorium and cerium
xenotime - a brown-to-yellow mineral that is a phosphate of yttrium in crystalline form