Question

Why does atomic radii increases as we go down in the group ? While decreases as we move from left to right in the peiod.

Answer 1

here is your answer:
as we move from top to bottom in a group the valance electron remains same but the number of shells goes on increasing due to which atomic radii increases.

along a period the number of shells remain same but the number of valance electron goes on increasing which increases the force of attraction and hence the atomic size decreases.

hope it helped !!