- Both the molecules have a pyramidal shape with a lone pair of electrons on the nitrogen atom.
- Although fluorine is more electronegative than nitrogen, the resultant dipole moment of NH3 (4.90×10−30 CM) is greater than that of NF3 (0.8×10−30 Cm).
- This is because in case of NH3 the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the N - H bonds.
- Whereas in NF3 the orbital dipole is in the direction opposite to the resultant dipole moment of the three N - F bonds. The orbital dipole because of the lone pair decreases the effect of the resultant N - F bond moments, which results in the low dipole moment of NF3.