Question

Consider the following
Assertion (A): Dipole moment of NF\(_3\) is lesser than NH\(_3\)
Reason (R): In NF\(_3\), the orbital dipole due to lone pair of electrons is in the opposite direction to the resultant dipole moment of the three N-F bonds.
The correct answer is:

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct, but (R) is not correct
• D. (A) is not correct, but (R) is correct

Hint:

Compare both the bond dipole directions and lone pair effects to determine net molecular dipole moments.

Answer 1

The Correct Option is A

- In NH\(_3\), the dipole moments of the N–H bonds add up due to the trigonal pyramidal shape, leading to a relatively strong dipole.
- In NF\(_3\), although F is more electronegative than H, the lone pair on nitrogen contributes a dipole opposite to the resultant N–F bond dipole.
- This opposition reduces the net dipole moment in NF\(_3\) compared to NH\(_3\).
- Hence, both the assertion and reason are correct, and the reason explains the assertion.