Which of the following has the highest value for bond order – C6H6, CO3^2-, NO^-, and SO3? A. C6H6 B. CO3^2- C. NO^- D. SO3
The Correct Answer and Explanation is:
Correct Answer: C. NO⁻
Explanation:
To determine which molecule or ion has the highest bond order, we need to understand how bond order is calculated. Bond order is the number of chemical bonds between a pair of atoms. A higher bond order means stronger and shorter bonds.
Bond order can be estimated using the formula:
Bond Order = (Number of bonding electrons – Number of antibonding electrons) ÷ 2
Let’s analyze each species:
1. C₆H₆ (Benzene):
In benzene, there are six carbon atoms forming a ring with alternating single and double bonds. However, due to resonance, all carbon-carbon bonds are equivalent.
Bond Order = (3 double bonds over 6 bonds) = 1.5
2. CO₃²⁻ (Carbonate ion):
This ion has one carbon and three oxygen atoms. There are three resonance structures where the double bond rotates among the three C–O bonds.
Bond Order = (1 double bond shared among 3 bonds) = 1.33
3. NO⁻ (Nitrosyl anion):
Nitric oxide (NO) has 11 valence electrons. Adding one more electron for the anion gives 12 total. According to molecular orbital theory, this gives a bond order of:
Bond Order = (8 bonding electrons – 2 antibonding electrons) ÷ 2 = 3.0
4. SO₃ (Sulfur trioxide):
SO₃ has three resonance structures. Each S–O bond is equivalent due to delocalization of electrons.
Bond Order = (2 double bonds shared among 3 bonds) = 1.33
Conclusion:
Among the given species, NO⁻ has the highest bond order of 3, indicating the strongest and shortest bond.
Thus, the correct choice is C. NO⁻.
