Dipole moment of NF₃ is smaller than: 

Solution:

• 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 NF_3​ 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​.