Which of the following statement regarding $NH_{3}$ and $NF_{3}$ is correct?
A$NH_{3}$ has pyramidal and $NF_{3}$ has trigonal planar shape.
BBond angle in $NH_{3}$ is smaller than $NF_{3}$ .
CResultant dipole moment of $NH_{3}$ is $(4.90 \times 10^{-30} \, \text{cm})$ and that of $NF_{3}$ is $(0.8 \times 10^{-30} \, \text{cm})$ .
DThey both are $sp^2$ hybridised.
Answer & Solution
Correct answer: C. Resultant dipole moment of $NH_{3}$ is $(4.90 \times 10^{-30} \, \text{cm})$ and that of $NF_{3}$ is $(0.8 \times 10^{-30} \, \text{cm})$ .
Both $NH_3$ and $NF_3$ are pyramidal and $sp^3$ hybridised, so A and D are incorrect. In $NF_3$, the bond moments oppose the lone-pair moment more strongly, so its net dipole moment is much smaller than that of $NH_3$; therefore B is also wrong because bond angle in $NF_3$ is smaller. Hence option C is correct.
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