Question

Halides of $III$A group element predominantly acts as?
A.Lewis base
B.Lewis acid
C.Arrhenius acid
D.Neutral halide

Answer 1

Hint: The halides of $III$ are present in the p block, because the electrons are filled till the p orbit.

Complete answer:
Halides of $III$A group in a trivalent state only have $6$electrons in their orbit. In order to complete their orbit they tend to receive electrons. This completes their octet state. Lewis bases tend to donate electrons since they are electron rich. They occupy higher orbit molecular states and hence have a tendency to donate. While Lewis acid has an orbit that is empty and can be filled. Hence they are called electron receiving groups. Since halide $III$A displays the same quality they act as Lewis base. Arrhenius acids tend to form salt and water in any reaction by giving ${H^ + }$ions . And since the halides are receiving electrons they are not neutral and hence cannot act as a neutral halide. Therefore they show the properties of Lewis acid.

Hence, option B Lewis acid

Note:
Along with onium ions ${H^ + }$ions can be considered as Lewis acid. Basically any electron deficient atom can act as a Lewis acid. Trigonal planar elements tend to accept electrons too making it act like Lewis acid.