Caesium

3 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  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]

From WordNet (r) 2.0 [wn]:

  caesium
       n : a soft silver-white ductile metallic element (liquid at
           normal temperatures); the most electropositive and
           alkaline metal [syn: {cesium}, {Cs}, {atomic number 55}]

From Elements database 20001107 [elements]:

  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.