Question

Which of the following statements about the 13th group elements is correct?

• A. Boron, unlike $Al$ and $Ga$, dissolves in conc. $HN{O}_3$ forming $H_{3}B{O}_3$
• B. Boron does not exhibit allotropy
• C. $B{F}_3$ is a better lewis acid than $BB{r}_3$
• D. The trend of atomic radii is as follows: $B<Al<Ga<In<Tl$

Answer 1

The correct option is A Boron, unlike $Al$ and $Ga$, dissolves in conc. $HN{O}_3$ forming $H_{3}B{O}_3$

$Al$ and $Ga$ form a passive inert oxide layer on the surface to impede the attack of the acid, whereas $B$, dissolves.

Boron is known to exhibit allotropy.

$B{F}_3$ is a weaker lewis acid than $BB{r}_3$ due to the backbonding between the flourine atom and the central boron atom. This reduces the electropositivity of the central boron atom.

The trend for atomic radii is as follows: $B<Ga<Al<In<Tl$

$Ga$ is smaller than $Al$ due to poor shielding of the d-orbitals giving it a greater effective nuclear charge and hence, a smaller radius.