The electronegativity difference between N and F is greater than that between N and H, yet the dipole moment of NH₃ (1.5 D) is larger than that or NF₃ (0.2 D). This is because :

In NH₃ as well as in NF₃ the atomic dipole and bond dipole are in the same direction

In NH₃ the atomic dipole and bond dipole are in the opposite directions, whereas in NF₃ these are in the same direction

In NH₃ as well as NF₃ the atomic dipole and bond dipole are in opposite directions

In NH₃ the atomic dipole and bond dipole are in the same direction, whereas in NF₃ these are in opposite directions