Dipole moment of NF_3 is smaller than

MCQ

Dipole moment of $NF_3$ is smaller than

✓
$NH_3$
B
$CO_2$
C
$BF_3$
D
$CCl_4$

✓

Answer

Correct option: A.

$NH_3$

a
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 $\mathrm{NH}_{3}\left(4.90 \times 10^{-30} \mathrm{CM}\right)$ is greater than that of $\mathrm{NF}_{3}\left(0.8 \times 10^{-30} \mathrm{Cm}\right)$

This is because in case of $\mathrm{NH}_{3}$ the orbital dipole due to lone pair is in the same direction as the

resultant dipole moment of the $\mathrm{N}-\mathrm{H}$ bonds. Whereas in $\mathrm{NF}_{3}$ 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 $\mathrm{NF}_{3}$.