thallium

American  

[thal-ee-uhm] / ˈθæl i əm /

noun

Chemistry.

1. a soft, malleable, rare, bluish-white metallic element: used in the manufacture of alloys and, in the form of its salts, in rodenticides. Tl; 204.37; 81; 11.85 at 20°C.

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thallium British  

/ ˈθælɪəm /

noun

1. a soft malleable highly toxic white metallic element used as a rodent and insect poison and in low-melting glass. Its compounds are used as infrared detectors and in photoelectric cells. Symbol: Tl; atomic no: 81; atomic wt: 204.3833; valency: 1 or 3; relative density: 11.85; melting pt: 304°C; boiling pt: 1473±10°C

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thallium Scientific  

/ thăl′ē-əm /

1. A soft, malleable, very poisonous metallic element that is used in photography, in making low-melting and highly refractive glass, and in treating skin infections. Atomic number 81; atomic weight 204.38; melting point 303.5°C; boiling point 1,457°C; specific gravity 11.85; valence 1, 3.

2. See Periodic Table

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Etymology

Origin of thallium

1860–65; < New Latin, equivalent to thall- (< Greek thallós green stalk) + -ium -ium; named after green line in its spectrum

Example Sentences

The 8th century Katla eruption created a 12-year spike in metals like bismuth and thallium in Greenland ice cores.

From Science Daily • Mar. 20, 2026

The thallium isotope ratios showed the global ocean lost oxygen overall during the last ice age compared to the current warmer interglacial period.

From Science Daily • Jan. 21, 2024

Lepidolite extraction and smelting produces toxic by-products like thallium and tantalum that cause severe water pollution, said Wu Wei, an assistant professor at Xiamen University.

From Reuters • Jun. 15, 2023

While analysing Miyamoto's smartphone, police found internet searches for thallium from before the time Hamano was hospitalised.

From BBC • Mar. 27, 2023

With the exception of lead and thallium the quantity of metal deposited from an acid solution is always greater than that of the peroxide.

From Scientific American Supplement, No. 441, June 14, 1884. by Various