Polarity of Ammonia (NH3)
Ammonia (NH3) has three single covalent bonds formed between the central nitrogen (N) atom and the three hydrogen (H) atoms. Lewis structure confirms a pair of nonbonding electrons on the nitrogen. Lone pairs affect polarity and contribute to the localized negative charges on the atom. The lone pair on nitrogen exerts outward force on the bonds in a trigonal pyramidal structure with a bond angle of 107°. The shape of NH3 is asymmetric, which means that the molecule is polar and has a net dipole moment.
The difference between the electronegativities of nitrogen (3.04) and hydrogen (2.18) is relatively high (0.86), making the N-H bond highly polar. This vast difference in the electronegativities leads to three dipole moments. Because of the asymmetrical shape, these three moments do not cancel and result in a net dipole moment. The charges are unequally distributed, making ammonia polar.