thallium

• POS: Noun
• HYPHEN: thal=li=um

CIDE DICTIONARY

thallium, n. [NL., fr. Gr. young or green shoot or branch, twig. So called from a characteristic bright green line in its spectrum.].

 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]

OXFORD DICTIONARY

thallium, n. Chem. a rare soft white metallic element, occurring naturally in zinc blende and some iron ores.

Derivative

thallic adj. thallous adj.

Etymology

formed as THALLUS, from the green line in its spectrum