Question

Incorrect order of atomic radius is

• A. \( \mathrm{B<Al} \)
• B. \( \mathrm{In<Tl} \)
• C. \( \mathrm{Al<Ga} \)
• D. \( \mathrm{Ga<In} \)

Hint:

While atomic radius usually increases down a group, exceptions like \( \mathrm{Ga} \) and \( \mathrm{Tl} \) occur because of poor shielding by \( d \)- and \( f \)-electrons. Always remember d-block contraction and lanthanoid contraction for such comparisons.

Answer 1

The Correct Option is C