Specifications: Caesium Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft silvery-gold alkali metal with a melting point of 28 ¡C (83 ¡F), which makes it one of the metals that are liquid at or near room temperature, along with rubidium (39 ¡C [102 ¡F]), This element is most notably used in atomic clocks. The variant spelling cesium is used especially in North American English, but caesium is the spelling used by the IUPAC.
