Question

Explain the trend of the following in group 13 elements:

Atomic radii

Answer 1

1. In group 13, on moving down the group, the atomic radii increases from B to Al.
2. However, there is an anomaly observed in the atomic radius of gallium due to the presence of 3d electrons. These inner 3d electrons offer a poor shielding effect and thus, valence shell electrons of Ga experience greater nuclear attraction. As a result, the atomic radius of gallium is less than that of aluminium.
3. However, the atomic radii again increase from Ga to Tl.
4. Therefore, the atomic radii of the group 13 elements vary in the following order:
   B < Al > Ga < In < Tl