Recognition and Extraction of Cesium Hydroxide and Carbonate using a Neutral Multitopic Ion-Pair Receptor.

See more Cesium products. Cesium (or Caesium) (atomic symbol: Ce, atomic number: 55) is a Block S, Group 1, Period 6 element with an atomic weight of 132.9054519. The number of electrons in each of Cesium's shells is 2, 8, 18, 18, 8, 1 and its electron configuration is [Xe]6s¹. The cesium atom has a radius of 265 pm and a Van der Waals radius of 343 pm. Cesium is a member of the alkali group of metals. It is one of three metals that occur as a liquid at room temperature, the others being mercury and gallium. Cesium's main commercial source is pollucite ore; however, it is also found in beryl, avogadrite, pezzottaite, and londonite. Cesium was discovered by Robert Bunsen and Gustav Kirchhoff in 1860 and first isolated by Carl Setterberg in 1882. In its elemental form, cesium has a silvery gold appearance. The word Cesium originates from the Latin word "caesius," meaning "sky blue," which refers to the vibrant blue lines in its spectrum.