Ammonia is formed from 3 atoms of Hydrogen and 1 atom of Nitrogen.
Atomic number of N = 7
Electronic configuration = 2, 5
Atomic number of H = 1
Electronic configuration = 1
So hydrogen needs 1 more electron to complete its duplet and nitrogen needs three more electrons to complete its octet
Hence, three hydrogen atoms each share their 1 electron with nitrogen to form three covalent bonds and make an ammonia molecule (NH3) ammonia molecule.