Question

Why do atomic radius increase in a group from top to bottom?

Answer 1

This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron; thus, electrons are pulled towards the nucleus, resulting in a smaller radius.Atomic radius increases from top to bottom within a group. This is caused by electron shielding.

Answer 2

As we descend the group, the principal quantum number (n) increases and the valance electrons are farther from the nucleus.

Bcoz, the inner energy levels are filled with electrons, which serves the shield the outer electrons from the pull of the nucleus. Consequently the size of the atom increases as reflected in the atomic radii.

Hope you understand