Therefore, moving left to right across a period the nucleus has a greater pull on the outer electrons and the atomic radii decreases. Moving down a group in the periodic table, the number of filled electron shells increases
In a group, when we move down from top to bottom then there occurs an increase in atomic size due to addition of electrons into the new shells of elements.
For example, lithium and cesium are same group elements. Atomic radius of lithium is 182 pm and atomic radius of cesium is 343 pm.
Whereas when we move across a period then there occurs a decrease in atomic radius of the atoms due to addition of electrons into the same shell.
Therefore, we can conclude that as you move from top to bottom on the periodic table, the atomic radius of the atoms increase.
