A bonding molecular orbital has lesser energy than the corresponding antibonding molecular orbital. Justify

Answer

To justify why a bonding molecular orbital has lesser energy than the corresponding antibonding molecular orbital, we can follow these steps:

### Step 1: Understanding Molecular Orbitals
Molecular orbitals are formed when atomic orbitals combine. There are two types of molecular orbitals: bonding and antibonding.

### Step 2: Formation of Bonding and Antibonding Orbitals
- **Bonding Molecular Orbital (BMO)**: This is formed by the constructive interference of atomic orbitals, which means the wave functions of the atomic orbitals add together. This results in an orbital that has a higher electron density between the nuclei of the bonding atoms, leading to a stabilizing effect.

- **Antibonding Molecular Orbital (AMO)**: This is formed by the destructive interference of atomic orbitals, where the wave functions subtract from each other. This results in a node (a region of zero electron density) between the nuclei, which destabilizes the molecule.

### Step 3: Energy Considerations
- The bonding molecular orbital is more stable because it has a higher electron density between the nuclei, which leads to a stronger attraction between the electrons and the nuclei. This stability corresponds to lower energy.

- Conversely, the antibonding molecular orbital is less stable due to the presence of a node and lower electron density between the nuclei, leading to a weaker attraction and thus a higher energy.

### Step 4: Conclusion
In summary, the bonding molecular orbital is lower in energy than the antibonding molecular orbital because the bonding orbital results from the addition of wave functions (constructive interference), leading to stability and lower energy, while the antibonding orbital results from the subtraction of wave functions (destructive interference), leading to instability and higher energy.

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