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caesium n. 銫[金屬元素] 銫[金屬元素] caesium n 1: a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal [synonym: {cesium}, {caesium}, {Cs}, {atomic number 55}] caesium \caesium\, Caesium \C[ae]"si*um\(s[=e]"z[-e]*[u^]m), n. [NL., from L. caesius bluish gray.] (Chem.) A rare alkaline metal found in mineral water; -- so called from the two characteristic blue lines in its spectrum. It was the first element discovered by spectrum analysis, and is the most strongly basic and electro-positive substance known. Symbol Cs. Atomic number 55. Atomic weight 132.6. Syn: cesium, Cs [1913 Webster] caesium
Symbol: Cs Atomic number: 55 Atomic weight: 132.90545 Soft silvery-white metallic element belonging to group 1 of the periodic table. One of the three metals which are liquid at room temperature. Cs-133 is the natural, and only stable, isotope. Fifteen other radioisotopes exist. Caesium reacts explosively with cold water, and ice at temperatures above 157K. Caesium hydroxide is the strongest base known. Caesium is the most electropositive, most alkaline and has the least ionization potential of all the elements. Known uses include the basis of atomic clocks, catalyst for the hydrogenation of some organic compounds, and in photoelectric cells. Caesium was discovered by Gustav Kirchoff and Robert Bunsen in Germany in 1860 spectroscopically. Its identification was based upon the bright blue lines in its spectrum. The name comes from the latin word caesius, which means sky blue. Caesium should be considered highly toxic. Some of the radioisotopes are even more toxic.
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