Question
Which of the two - NH3 and NF3 has higher dipole moment and why?
Solution
NH3 has a higher dipole moment. Both these molecules have the pyramidal shape with one lone pair.
In the case of NH3, the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the three N – H bonds. Therefore, it adds on the resultant of the N – H bonds. But in a case of 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. Thus the lone pair moment cancels the resultant N – F bond moment. Consequently, the dipole moment of NF3 is low.
