Question

Dipole moment of $N{F}_3$ is smaller than:

• A. $N{H}_3$
• B. $C{O}_2$
• C. $B{F}_3$
• D. $CC{l}_4$

Answer 1

The correct option is A $N{H}_3$

• 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 $N{H}_3(4.90\times {10}^{-30}CM)$ is greater than that of $N{F}_3(0.8\times {10}^{-30}Cm).$
• This is because in case of $N{H}_3$ the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the N - H bonds.
• Whereas in $N{F}_3$ 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 $N{F}_3$.