Caesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold 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..

Atomic Weight: 243
Density:       353.3 g/cm3
Melting Point: 345
Boiling Point: 346