How does the atomic radius of the elements change on going (i) from left to right in a period, and (ii) down a group in the Modern Periodic Table? Give reason in support of your answer.
As we go from left to right in a period,
- The nuclear charge increases but the number of shells increases
so this tends to pull the electrons closer to the nucleus and atomic radius decreases.
As we move down a group,
- The number of shells increases , the electrostatic attraction between the nucleus and the outermost shell electrons decreases and so, the atomic radius increases.