Cesium is a chemical element and its symbol is Cs. The atomic number of cesium is 55. Cesium is an alkali metal with atomic weight is equal to 132.9 grams per mole. The color of cesium is silvery gold. It belongs to the 's' block and 6th period of the periodic table. It is present in first group of the periodic table so, it has only one electron in its outer most shell. The electronic configuration of cesium is 6s1. The electrons in per shell of an atom of cesium are 2, 8, 18, 18, 8 and 1. Cesium atom loses one electron to combine with other atoms and to become stable. When a cesium atom loses one charge, its outer most shell is filled and it becomes a positive ion.