Bonding Molecular Orbitals (BMO):
- Formed when atomic orbitals combine constructively (their wave functions add).
- Electrons in these orbitals hold atoms together, increasing stability.
- Energy of bonding orbitals is lower than the original atomic orbitals.
- Example: In H₂, the combination of two 1s orbitals forms a σ (sigma) bonding orbital.
Anti-Bonding Molecular Orbitals (ABMO):
- Formed when atomic orbitals combine destructively (their wave functions subtract).
- Electrons in these orbitals weaken the bond and reduce stability.
- Energy of anti-bonding orbitals is higher than the original atomic orbitals.
- Indicated by a “*” (star), e.g., σ* or π*.
Summary:
- Bonding orbitals → lower energy → stabilize the molecule.
- Anti-bonding orbitals → higher energy → destabilize the molecule.