thallium

Definition

A metallic chemical element (symbol Tl) with atomic number 81: a gray post-transition metal that discolors when exposed to air.

Etymology

Coined based on Ancient Greek θαλλός (thallós, “green branch”) (after the color of the radiation spectra), + -ium.

Example Sentences

• "Environmental authorities in Lüeyang County, Shaanxi province, discovered excessive levels of thallium in two of the Jialing River’s upstream tributaries on Jan. 20, according to a statement Monday. The concentration of thallium that day was 170% higher than the standard for Qingni River, one of the upstream tributaries bordering Gansu province."