[thal-ee-uh
m] 
| 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. |
| thal·li·um (thāl'ē-əm) n. Symbol Tl A soft, malleable, highly toxic metallic element, used in photocells, infrared detectors, low-melting glass, and formerly in rodent and ant poisons. 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 Table at element. [thall(o)- (from its green spectral line) + -ium.] |
thallium thal·li·um (thāl'ē-əm)
n.
Symbol Tl
A soft, malleable, highly toxic metallic element, used in photocells, infrared detectors, and low-melting glass. Atomic number 81; atomic weight 204.38; melting point 303.5°C; boiling point 1,473°C; specific gravity 11.85; valence 1, 3.
thallium
(Tl), chemical element, metal of main Group IIIa, or boron group, of the periodic table, poisonous and of limited commercial value. Like lead, thallium is a soft, low-melting element of low tensile strength. Freshly cut thallium has a metallic lustre that dulls to bluish gray upon exposure to air. The metal continues to oxidize upon prolonged contact with air, generating a heavy nonprotective oxide crust. Thallium dissolves slowly in hydrochloric acid and dilute sulfuric acid and rapidly in nitric acid.
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