Question

Which of the following molecules posses more dipole moment and why?

${NH}_3$ or ${NF}_3$

Answer 1

In $N{H}_3$, N is more electronegative than H. So, N pulls the electrons from H towards itself and so the direction of the moment due to the N-H bonds is in the same direction as that of the lone pair of electrons on Nitrogen.

Whereas in $N{F}_3$, the electronegativity of the F is more than N, thus the dipole moment of the bond pairs of electrons between N and F is towards F. But the dipole moment of the lone pair of electrons of N is opposite to the dipole moment of a bond pair.

So, $N{H}_3$ posses more dipole moment than that of the $N{F}_3$