Thallium

3 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Thallium \Thal"li*um\, n. [NL., fr. Gr. ? young or green shoot
     or branch, twig. So called from a characteristic bright green
     line in its spectrum.] (Chem.)
     A rare metallic element of the aluminium group found in some
     minerals, as certain pyrites, and also in the lead-chamber
     deposit in the manufacture of sulphuric acid. It is isolated


     as a heavy, soft, bluish white metal, easily oxidized in
     moist air, but preserved by keeping under water. Symbol Tl.
     Atomic weight 203.7.
     [1913 Webster]

From WordNet (r) 2.0 [wn]:

  thallium
       n : a soft gray malleable metallic element that resembles tin
           but discolors on exposure to air; it is highly toxic and
           is used in rodent and insect poisons; occurs in zinc
           blende and some iron ores [syn: {Tl}, {atomic number 81}]

From Elements database 20001107 [elements]:

  thallium
  Symbol: Tl
  Atomic number: 81
  Atomic weight: 204.3833
  Pure, unreacted thallium appears silvery-white and exhibits a metallic
  lustre. Upon reacting with air, it begins to turn bluish-grey and looks
  like lead. It is very malleable, and can be cut with a knife. There are
  two stable isotopes, and four radioisotopes, Tl-204 being the most stable
  with a half-life of 3.78 years. Thallium sulphate was used as a rodenticide.
  Thallium sulphine's conductivity changes with exposure to infrared light,
  this gives it a use in infrared detectors. Discovered by Sir William Crookes
  via spectroscopy. Its name comes from the Greek word thallos, which means
  green twig. Thallium and its compounds are toxic and can cause cancer.