Question

In which one of the following pairs does the stability of the monovalent ion increase with respect to the molecule, while the magnetic character remains the same for both?

• A. \(C_2/C_2^+\)
• B. \(O_2/O_2^+\)
• C. \(B_2/B_2^+\)
• D. \(N_2/N_2^+\)

Hint:

Removal of electrons from antibonding orbitals increases bond order and stability.

Answer 1

The Correct Option is B

Step 1: Recall stability criterion.
Stability is determined by bond order:
\[ \text{Bond Order} = \frac{N_b - N_a}{2} \]
Higher bond order means greater stability.

Step 2: Analyse \(O_2\).
Electronic configuration gives bond order:
\[ BO(O_2)=2 \]
It has two unpaired electrons, so it is paramagnetic.

Step 3: Analyse \(O_2^+\).
Removal of one electron from antibonding orbital increases bond order:
\[ BO(O_2^+)=2.5 \]
It still has one unpaired electron, so it remains paramagnetic.

Step 4: Compare stability.
Since bond order increases from 2 to 2.5:
\[ O_2^+ \text{ is more stable than } O_2. \]

Step 5: Check magnetic character.
Both \(O_2\) and \(O_2^+\) are paramagnetic.
Hence, magnetic character remains same.

Step 6: Check other options briefly.
Other molecules either change magnetic nature or do not show increase in bond order.

Step 7: Final conclusion.
\[ \boxed{O_2/O_2^+} \]