thallium

[thal-ee-uh m]
noun Chemistry.
  1. a soft, malleable, rare, bluish-white metallic element: used in the manufacture of alloys and, in the form of its salts, in rodenticides. Symbol: Tl; atomic weight: 204.37; atomic number: 81; specific gravity: 11.85 at 20°C.

Origin of thallium

1860–65; < New Latin, equivalent to thall- (< Greek thallós green stalk) + -ium -ium; named after green line in its spectrum
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for thallium

thallium

noun
  1. a soft malleable highly toxic white metallic element used as a rodent and insect poison and in low-melting glass. Its compounds are used as infrared detectors and in photoelectric cells. Symbol: Tl; atomic no: 81; atomic wt: 204.3833; valency: 1 or 3; relative density: 11.85; melting pt: 304°C; boiling pt: 1473±10°C

Word Origin for thallium

C19: from New Latin, from Greek thallos a green shoot; referring to the green line in its spectrum
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for thallium
n.

rare metallic element, 1861, Modern Latin, from Greek thallos "young shoot, green branch" (see thallus) + element name ending -ium. So called by its discoverer, Sir William Crookes (1832-1919), from the green line in its spectrum by which he detected it.

Online Etymology Dictionary, © 2010 Douglas Harper

thallium in Medicine

thallium

[thălē-əm]
n. Symbol Tl
  1. A soft, malleable, highly toxic metallic element whose radioisotopes are used in diagnostic imaging. Atomic number 81.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

thallium in Science

thallium

[thălē-əm]
Tl
  1. A soft, malleable, very poisonous metallic element that is used in photography, in making low-melting and highly refractive glass, and in treating skin infections. Atomic number 81; atomic weight 204.38; melting point 303.5°C; boiling point 1,457°C; specific gravity 11.85; valence 1, 3. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.