The correct order of atomic radii in group 13 elements is

In III group, from top to bottom, atomic size gradually increases due to increase in atomic number, and electrons enters into new shell. So, the order is B < Al < Ga < In < Tl. However, actual order is B < Ga < Al < In < Tl
due to poor shielding effect of d-orbitals in Ga. So, atomic radii of Ga is less than Al.
(1) B < Al < In < Ga < Tl - Density order In third group, boron has lowest atomic radii and lowest density.