Question

The total number of anti bonding molecular orbitals, formed from 2s and 2p atomic orbitals in a diatomic molecule is _____________.

Answer 1

Correct Answer: 4

In a diatomic molecule, when combining atomic orbitals, both bonding and anti-bonding molecular orbitals are formed. For atomic orbitals 2s and 2p: 

• Combination of 2s orbitals: When two 2s orbitals overlap, they form one bonding (σ_2s) and one anti-bonding (σ_2s^*) molecular orbital.
• Combination of 2p orbitals: The 2p orbitals split into three types: σ and two π orbitals. This results in bonding and anti-bonding combinations:
  • σ_2p orbitals: Form one σ_2p and one σ_2p^* orbital.
  • π_2p orbitals: Each set forms two degenerate π_2p and π_2p^* orbitals. Since there are two sets, this results in two bonding π_2p orbitals and two antibonding π_2p^* orbitals.

Total number of anti-bonding orbitals:

• From 2s: 1 σ_2s^* orbital.
• From 2p: 1 σ_2p^* and 2 π_2p^* orbitals.

Total anti-bonding orbitals = 1 (from 2s) + 1 (from σ_2p^*) + 2 (from 2 π_2p^*) = 4.
This total, 4, falls within the given range (4,4).

Answer 2

In molecular orbital theory, the anti-bonding molecular orbitals formed from atomic orbitals are as follows:

- Anti-bonding molecular orbital from 2s: 1  
- Anti-bonding molecular orbitals from 2p: 3  

Thus, the total number of anti-bonding molecular orbitals is:  
\(1 + 3 = 4\)

The Correct Answer is: 4