Write about cesium atom?

     

Caesium is also called as Cesium (in American English) is a chemical element with the symbol Cs and atomic number 55.  It is ka soft, silvery-golden alkali metal with a melting point of 28.5C which makes it one of only five elemental metals that are liquid at or near room temperature.  Cesium has physical and chemical properties similar to those of rubidium and potassium.  The most reactive of all metals, it is pyrophoric and reacts with water even at -116C.  It is the least electronegative element, with a value of 0.79 on the Pauling scale.  It has only one stable isotope, cesium-133.

     Cesium is mined mostly from pollucite, while the radioisotopes, especially cesium 137, a fission product, are extracted from waste produced by nuclear reactors.  The German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered cesium in 1860 by the newly developed method of flame spectroscopy.  The first small-scale applications for cesium were as a "getter" in 1967, acting on Einstein's proof that the speed of light is the most constant dimension in the universe, the international System of Units used two specific wave counts from an emission spectrum of cesium 133 to codefine the second and the metre. 

     Since the 1990s the largest application of the element has been as cesium formate for drilling fluids, but it has a range of applications in the production of electricity, in electronics, and in chemistry.  The radiocactive isotope cesium 137 has a  half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology.