Question

Why do ammonia act as lewis base

Answer 1

a lewis acid is an electron-pair acceptor and a lewis base is an electron pair donor.NH3 or ammonia has a formal lane of electrons on the nitrogen atom...
because N atom contain a lone pair of electrons NH3 acts as a lewis base.........

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.