In a molecule of NH3 , how many lone pairs are the on the nitrogen atom?(Remember that one lone pair = two electrons).

Ammonia (NH3) has one nitrogen atom and three hydrogen atoms.

1. Nitrogen (N) is in group 15 of the periodic table and therefore has 5 valence electrons.
2. Hydrogen (H) is in group 1 of the periodic table and therefore has 1 valence electron. Since there are three hydrogen atoms in the molecule, we multiply 1 by 3 to get 3.

When nitrogen forms covalent bonds with the three hydrogen atoms, it shares one electron with each hydrogen atom. This accounts for 3 of nitrogen's 5 valence electrons, leaving 2 electrons unaccounted for.

These 2 remaining electrons on the nitrogen atom are not shared with another atom, so they exist as a lone pair.

So, there is 1 lone pair on the nitrogen atom in a molecule of NH3.