Question

Which one of the following pairs of species have the same bond order?

• A. CO, NO
• B. O₂, NO⁺
• C. CN^–, CO
• D. N₂, O₂^-

Answer 1

The Correct Option is C

To determine which pair of species has the same bond order, we first need to understand the concept of bond order. Bond order is a measure of the stability of a bond and can be determined from the molecular orbital (MO) theory. Higher bond orders generally correspond to shorter, stronger bonds.

The bond order can be calculated using the formula:

\[ \text{Bond Order} = \frac{\text{Number of bonding electrons} - \text{Number of antibonding electrons}}{2} \]

Now, let's calculate the bond order for each of the species provided:

1. CO: The electronic configuration is similar to N₂, with a bond order of 3.
2. NO: The electronic configuration results in a bond order of 2.5.
3. O₂: The electronic configuration results in a bond order of 2.
4. NO⁺: With one less electron than NO, the bond order is 3.
5. CN^–: The electronic configuration is similar to CO, with a bond order of 3.
6. N₂: Known to have a bond order of 3.
7. O₂^-: With one extra electron, the bond order decreases to 1.5.

The pair CN^– and CO both have the same bond order of 3, making it the correct answer.

Conclusion: The pair of species with the same bond order are CN^– and CO. This is due to their similar electronic configurations that lead to equal bond order.