Question

Which of the following species have same bond order? I. \( \mathrm{H_2} \)
II. \( \mathrm{B_2} \)
III. \( \mathrm{O_2^{2-}} \)
IV. \( \mathrm{Be_2} \)
V. \( \mathrm{N_2} \)
Correct option is:

• A. I and II
• B. I, II and III
• C. I, II and IV
• D. I, IV and V

Hint:

Always remember: \( \mathrm{O_2^{2-}} \) has bond order 1 (like single bond).

Answer 1

The Correct Option is B

Concept: Bond order: \[ \text{B.O.} = \frac{N_b - N_a}{2} \] where \(N_b\) = bonding electrons, \(N_a\) = antibonding electrons.

Step 1: Calculate bond orders (I) \( \mathrm{H_2} \): \[ \text{B.O.} = 1 \] (II) \( \mathrm{B_2} \): Electronic configuration gives: \[ \text{B.O.} = 1 \] (III) \( \mathrm{O_2^{2-}} \): \[ \text{B.O.} = 1 \] (IV) \( \mathrm{Be_2} \): \[ \text{B.O.} = 0 \] (V) \( \mathrm{N_2} \): \[ \text{B.O.} = 3 \]

Step 2: Compare Species with same bond order: \[ \mathrm{H_2}, \mathrm{B_2}, \mathrm{O_2^{2-}} \quad (\text{all have B.O. = 1}) \] Final Answer: \[ {\text{I, II and III}} \]