Question

What is the bond order for diatomic carbon according to molecular orbital theory?

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

To calculate the bond order using molecular orbital theory, use the formula: \[ \text{Bond order} = \frac{N_b - N_a}{2} \] where \( N_b \) is the number of bonding electrons and \( N_a \) is the number of antibonding electrons.

Answer 1

The Correct Option is B

Step 1: Total valence electrons in C\(_2\) = 4 + 4 = 8.
Step 2: The 2s orbitals fill and cancel each other out \( (\sigma_{2s}^2\sigma_{2s}^{*2}) \), contributing zero net bonding.
Step 3: The remaining 4 electrons fill both pi orbitals \( (\pi_{2px}^2\pi_{2py}^2) \), giving 2 bonding pairs and no antibonding pairs among them.
Step 4: Bond order \[ = \frac{4-0}{2} = \boxed{2} \], matching option (B).