Which out of NH₃ and NF₃ has higher dipole moment and why?
NH₃ has a higher dipole moment ( C m) compared to NF₃ ( C m).
Both molecules have a pyramidal shape with a lone pair of electrons on the nitrogen atom. In the case of NH₃, the orbital dipole due to the lone pair is in the same direction as the resultant dipole moment of the three N–H bonds. This additive effect results in a higher net dipole moment.
Conversely, in NF₃, the orbital dipole due to the lone pair is in the opposite direction to the resultant dipole moment of the three N–F bonds. This opposite direction decreases the effect of the resultant N–F bond moments, resulting in a low net dipole moment for NF₃.
Explanation
The dipole moment of NH3 is greater than that of NF3. This is because in 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 lone pair decreases the effect of the resultant N–F bond moments, which results in the low dipole moment of NF3.