Question

Which of the following statement is not correct?

• A. Higher the lattice enthalpy, greater the stability of ionic compounds
• B. In $NF_{3}$, the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the N-F bonds.
• C. Br-Br bond length is greater than Cl-Cl bond length
• D. Dioxygen, dinitrogen molecules have different bond orders

Hint:

For dipole in NF3 vs NH3: EN difference affects direction. Bond order from MO theory: N2 (3), O2 (2). Lattice enthalpy from Born-Haber cycle. Bond lengths from periodic trends.

Answer 1

The Correct Option is B

1. Statement (1): Lattice enthalpy measures ionic bond strength; higher values indicate more stable compounds, correct.
2. Statement (3): Bond length increases down the group due to larger atomic radii; Br>Cl, correct.
3. Statement (4): O$_2$ bond order 2 (paramagnetic), N$_2$ 3 (diamagnetic), different, correct.
4. Statement (2): In NF$_3$, pyramidal shape; bond dipoles (N$^+$ to F$^-$) net from N to F plane; lone pair at N (positive end) opposes, reducing dipole moment compared to NH$_3$, so directions opposite, incorrect.
5. Thus, (2) is not correct.