so to complete its valence shell ( duplet) H+ ion need two electrons . Therefore H+ is an electron acceptor(electrophile). When the ammonia molecule combines with H+ ion by the donation of lone pair electron from N-atom (in ammonia) to H+ ion results in the formation of ammonium ion ,NH4+.

How is NH4 positive?

⇒ The ammonium ion, NH+4 , becomes positive . A covalent bond is formed by two atoms sharing a pair of electrons between the N and the 4th-H forming a Co-ordinate (dative covalent) bond . The hydrogen’s electron is left behind on the chlorine to form a negative chloride ion.

Why is H2CO trigonal planar?

The electron geometry of H2CO is also trigonal planar because there is no lone pair present on the central atom(carbon), hence, only bonded pair will be counted for determining the shape of H2CO.