largest atom on periodic table
What is the largest atom (in terms of volume not atomic mass or weight)? 9/21/99 Vocabulary atomic radius effective nuclear charge lanthanide contraction pm valence electron valence shell Cesium (Cs), tucked in the lower left hand corner of the table, has the largest known atoms.The atomic radius of Cs is given variously as 273.1 pm [1], 265 pm [2], 265.5 pm [3] or 260 pm [4].ubidium also has large atoms, but its atomic radius is almost 30 pm less than cesium's. Why are cesium atoms so big? Cesium has a large valence shell and a relatively low effective nuclear charge. The valence shell (the outer 'peel' of the atom) is largest in atoms at the bottom of the periodic table.