Thallium
CHEMICAL ELEMENT WITH SYMBOL TL AND ATOMIC NUMBER 81
Thalium; Tallium; Element 81; Thallous; Thallium-201 stress test; Thallium compounds; Tl (element); Thallium(I); Organothallium; Thallium compound; Compounds of thallium; History of thallium
·noun 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.