Question

why does NH3 act as Lewis base?

Answer 1

Since nitrogen has five electron in its outtermost orbit among these three are bonded to hydrogen in NH3 and two electron are left.
Acording to Lewis theory,compounds which donates electron are said to be bases.

Answer 2

$\huge\boxed{\underline{\mathcal{\red{A}\green{N}\pink{S}\orange{W}\blue{E}\purple{R}}}}$

• ❤.. Nitrogen atom in ${NH3}$ has one lone pair of electron which is available for donation.
• ❤.. Therefore, it acts as a Lewis base.