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cesium

(sē′zē əm)

noun

a soft, silver-white, ductile, metallic chemical element, one of the alkali metals and the most electropositive of all the elements: it ignites in air, reacts vigorously with water, and is used in photoelectric cells: symbol, Cs; at. no., 55: a radioactive isotope () with a half-life of 30.17 years is a fission product and is used in cancer research, radiation therapy, etc.

Origin: ModL, orig. neut. of L caesius, bluish-gray (< IE base *(s)kai-, bright > -hood): so named (1860) by Robert Wilhelm Bunsen because of the blue line seen in the spectroscope

See cesium in American Heritage Dictionary 4

also cae·si·um

noun Symbol Cs

A soft, silvery-white ductile metal, liquid at room temperature, the most electropositive and alkaline of the elements, used in photoelectric cells and to catalyze hydrogenation of some organic compounds. Atomic number 55; atomic weight 132.905; melting point 28.5°C; boiling point 690°C; specific gravity 1.87; valence 1. See Table at element.

Origin:

Origin: From Latin caesius, bluish gray (from its blue spectral lines)

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