Question

A group 13 element X reacts with chlorine gas to produce a compound $XC{l}_3$. $XC{l}_3$ is electron deficient and easily reacts with $N{H}_3$ to form $C{l}_{3}X\to N{H}_3\text{adduct}$; however, $XC{l}_3$ does not dimerize, X is:

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

Answer 1

The correct option is A $B$

The required 13 group element is Boron.

When it reacts with chlorine it form $BC{l}_3$
The reaction is as follow:

$2B+3C{l}_2\to 2BC{l}_3$

When it reacts with $N{H}_3$ then it forms adduct which can be represented as $BC{l}_3\leftarrow N{H}_3$ and with excess of ammonia it forms boron nitride.

$BC{l}_3+4N{H}_3\to BN+3N{H}_{4}Cl$

$BC{l}_3$ is elecctron deficient group but it does not form dimer like Al, Ga or In because its electron deficiency is complemented by the formation of coordinate bond between lone pair of electron of chlorine and empty unhybridized p-orbital of boron forming $p\pi -p\pi$ bonding.

Hence, the correct option is A