Question

Why do boron and aluminium halides behave as Lewis acids?

• A. Both halides $\left(M{X}_3\right)$ can accept electrons from a donor to complete their octet.
• B. Both halides $\left(M{X}_3\right)$ can donate a pair of electrons.
• C. Both halides $\left(M{X}_3\right)$ are covalent polymeric structures.
• D. Both halides $\left(M{X}_3\right)$ react with water to give hydroxides and HCI.

Answer 1

The correct option is A Both halides $\left(M{X}_3\right)$ can accept electrons from a donor to complete their octet.

Answer:- (A) Both halides can accept electrons from a donor to complete their octet.

$\because$ Lewis acid is defined as an electron-pair acceptor and both boron and aluminium in their tri-halides $\left(M{X}_3\right)$ possess six electrons in their valence shell.

Hence, to complete their octet, they can accept a lone pair of electrons.

Thus, both behave as Lewis acid.