JEE Main 2022 — Classification of Elements and Periodicity in Properties Question with Solution

The expected order of melting points of group 13 elements is $\mathrm{B}>\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}$.

But due to structural changes, melting point instead of decreasing, increases from Ga to Tl and Ga has the lowest melting point. Hence, the actual order is $\mathrm{B}>\mathrm{Al}>\mathrm{Tl}>\mathrm{In}>\mathrm{Ga}$

Melting point

$\mathrm{Al}\to 933 \mathrm{K}$

$\mathrm{Ga}\to 303 \mathrm{K}$

$\mathrm{In}\to 430 \mathrm{K}$

$\mathrm{Se}\to 490 \mathrm{K}$

Ga has low meting point and it is closer to metalloid in periodic table.