Out of `NH_(3)` and `NF_(3)` which has a higher Dipole moment?

Explanation

In both molecules i.e., `NH_(3)` and `NF_(3)`, the central atom (N) has a lone pair electron and there are three bond pairs. Hence, both molecules have a pyramidal shape. Since fluorine is more electronegative than hydrogen, it is expected that the net dipole moment of `NF_(3)` is greater than `NH_(3)`. However, the net dipole moment of `NH_(3)`(1.46 D) is greater than that of `NF_(3)` (0.24 D).
This can be explained on the basis of the directions of the dipole moments of each individual bond is `NF_(3)` and `NH_(3)`. These directions can be shown as :

Thus, the resultant moment of the N-H bonds add up to the bond moment of the lone pair ( the two being in the same directionn), whereas that of the three N-F bonds partly cancels the moment of the lone pair.
Hence, the net dipole moment of `NF_(3)` is less than that of `NH_(3)`