Generally the atomic and ionic radii increase with increase in atomic number down the group. But the atomic size of aluminium and gallium is almost the same. This is because

Options

A. the high nuclear charge of Ga and Tl
B. the intervening d and f electrons
C. high ionization energies of these elements
D. none of these

Answer

B

Explanation

Because of ineffective shielding of nuclear charge by d electrons in case of Ga, In and Tl due to which the valence electrons are tightly held.