Question

The increasing order of atomic radii of group $13$ elements is:

• A. $Al<Ga<In<Tl$
• B. $Ga<Al<In<Tl$
• C. $Al<In<Ga<Tl$
• D. $Al<Ga<Tl<In$

Answer 1

The correct option is B $Ga<Al<In<Tl$

As we move down a group, the atomic radii goes on increasing.
But due to the poor shielding of $d$ orbital in $Ga$, the atomic radius of $Ga$ is smaller than that of $Al$.
Thus, the order becomes: $Ga<Al<In<Tl$