Question

Given below are statements about some molecules/ions. Identify the CORRECT statements.
A. The dipole moment value of $\mathrm{NF_3}$ is higher than that of $\mathrm{NH_3}$.
B. The dipole moment value of $\mathrm{BeH_2}$ is zero.
C. The bond order of $\mathrm{O_2^{2-}}$ and $\mathrm{F_2}$ is same.
D. The formal charge on the central oxygen atom of ozone is $-1$.
E. In $\mathrm{NO_2}$, all the three atoms satisfy the octet rule, hence it is very stable.
Choose the correct answer from the options given below:

• A. A, B, C, D \& E
• B. B \& C only
• C. B, C \& D only
• D. A, C \& D only
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Hint:

Always check molecular geometry and electron count before deciding dipole moment and octet rule validity.

Answer 1

The Correct Option is C

Step 1: Analysing statement A.
$\mathrm{NH_3}$ has a higher dipole moment than $\mathrm{NF_3}$ due to stronger N–H bond polarity and vector addition. Hence, statement A is false.
Step 2: Analysing statement B.
$\mathrm{BeH_2}$ is linear and symmetrical, so its dipole moments cancel out. Hence, dipole moment is zero. Statement B is true.
Step 3: Analysing statement C.
Bond order of $\mathrm{O_2^{2-}}$ is 1 and bond order of $\mathrm{F_2}$ is also 1. Hence, statement C is true.
Step 4: Analysing statement D.
In ozone $(\mathrm{O_3})$, the central oxygen atom has a formal charge of $-1$. Hence, statement D is true.
Step 5: Analysing statement E.
$\mathrm{NO_2}$ is an odd-electron molecule and does not satisfy the octet rule. Hence, statement E is false.
Step 6: Final conclusion.
Correct statements are B, C and D only, corresponding to option (3).