Get the details behind our redesign
cesium ce·si·um or cae·si·um (sē'zē-əm)
A soft ductile metal, liquid at room temperature, the most electropositive and alkaline of the elements, used in photoelectric cells. Atomic number 55; atomic weight 132.905; melting point 28.4°C; boiling point 671°C; specific gravity 1.87; valence 1.
A soft, ductile, silvery-white element of the alkali group. It is liquid at room temperature and is the most reactive of all metals. Cesium is used to make photoelectric cells, electron tubes, and atomic clocks. Atomic number 55; atomic weight 132.905; melting point 28.5°C; boiling point 690°C; specific gravity 1.87; valence 1. See Periodic Table.