Here’s a explanation of non-bonding molecular orbitals (NBMOs):
1. Definition
- Non-bonding molecular orbitals are molecular orbitals that contain electrons but do not contribute to bonding or antibonding between atoms.
- Electrons in these orbitals stay mostly on one atom rather than being shared between atoms.
2. Characteristics
- Energy is similar to the atomic orbital from which it originated.
- Electrons in non-bonding orbitals do not stabilize or destabilize the molecule significantly.
- Denoted as n in molecular orbital diagrams.
3. Examples
- Water (H₂O):
- Oxygen has lone pair electrons that occupy non-bonding orbitals.
- Ammonia (NH₃):
- Nitrogen’s lone pair occupies a non-bonding orbital.
4. Importance
- Non-bonding electrons influence:
- Molecular shape (via VSEPR theory)
- Polarity of molecules
- Chemical reactivity (e.g., lone pairs can act as nucleophiles)
- Spectroscopic properties (e.g., n → π* transitions in UV-Vis spectroscopy)
In short:
- Bonding MOs → stabilize molecule
- Antibonding MOs → destabilize molecule
- Non-bonding MOs → neutral, just hold lone pair electrons