Question

Select correct statements(s) (A) $\text{NF}_3$ has more dipole moment than $\text{NH}_3$ (B) $\text{O}_2^{2-}$ and $\text{F}_2$ both have same bond order (C) In $\text{O}_3$ central oxygen atom has $+1$ formal charge (D) In $\text{NO}_2$ all the atoms follow octet rule, so it is stable. (E) $\text{BeH}_2$ is planar

• A. B, C
• B. A, B, C
• C. C, D, E
• D. B, E

Hint:

Pay close attention to dipole moment cancellation in pyramidal molecules ($\text{NF}_3$ vs $\text{NH}_3$). Use $\text{MO}$ theory for accurate bond order comparison of diatomic species.

Answer 1

The Correct Option is D

Let's analyze each statement to determine the correct options:

• (A) $\text{NF}_3$ has more dipole moment than $\text{NH}_3$:
  This statement is incorrect. $\text{NH}_3$ has a higher dipole moment than $\text{NF}_3$. This is because $\text{NH}_3$ has a pyramidal structure with nitrogen being more electronegative than hydrogen, resulting in a significant dipole. Meanwhile, in $\text{NF}_3$, although fluorine is more electronegative than nitrogen, the geometry and bond angle cause a lower net dipole moment compared to $\text{NH}_3$.
• (B) $\text{O}_2^{2-}$ and $\text{F}_2$ both have the same bond order:
  This statement is correct. The bond order of $\text{O}_2^{2-}$ (peroxide ion) is 1 because it has a single bond. Similarly, $\text{F}_2$ also has a bond order of 1, as it forms a single bond between the two fluorine atoms.
• (C) In $\text{O}_3$, the central oxygen atom has a $+1$ formal charge:
  This statement is correct. In the resonance structures of ozone ($\text{O}_3$), the central oxygen can occasionally bear a formal charge of $+1$ in one of its resonance forms.
• (D) In $\text{NO}_2$, all the atoms follow the octet rule, so it is stable:
  This statement is incorrect. $\text{NO}_2$ does not have all atoms following the octet rule because nitrogen in $\text{NO}_2$ is unstable with 7 electrons in its valence shell. It does not fulfill the octet, contributing to the overall reactivity and instability of the molecule.
• (E) $\text{BeH}_2$ is planar:
  This statement is correct. $\text{BeH}_2$ has a linear geometry with $\text{Be}$ at the center and two $\text{H}$ atoms, resulting in a planar arrangement due to its sp hybridization.

Based on the analysis above, the correct choices are B and E.