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The dipole moment of ammonia (NH3) is greater than that of nitrogen trifluoride (NF3). Why is this the case?

1. The dipole vectors in NH3 are oriented in the same direction.
2. The lone pair in NH3 contributes the highest dipole moment.
3. The dipole moments are μ = 1.4D for NH3 and μ = 0.23D for NF3, with fluorine being more electronegative than nitrogen.
4. None of these explanations are correct.

Correct answer: The dipole moments are μ = 1.4D for NH3 and μ = 0.23D for NF3, with fluorine being more electronegative than nitrogen.

Solution

In NH3, the dipole moment of the lone pair and N-H bonds add up, while in NF3, the dipole moment of the lone pair opposes the N-F bond dipoles, resulting in a lower net dipole moment.

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