thal·li·um /ˈθælɪəm/ 名詞
Thal·li·um n. 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.
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]
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.