Question

Which is a Lewis base?

• A. $B_2{H}_6$
  
• B. $BC{l}_3$
  
• C. $Al{H}_3$
• D. $N{H}_3$

Answer 1

The correct option is D $N{H}_3$

Lewis Concept (Electronic concept) :
Lewis acid - species which can accept an electron pair with the formation of a coordinate bond.
Lewis base - species which has a lone pair of electrons available for donation.
$N{H}_3$ already has a lone pair on nitrogen so it can donate a lone pair of electrons thus it does not act as a lewis base.
Except $N{H}_3$, all have vacant orbital to accept lone pair electrons thus they can act as lewis acid. Hence correct option is d.