Which types of orbitals stabilize a molecule ?

Answer

To answer the question "Which types of orbitals stabilize a molecule?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Molecular Orbitals**:
- Molecular orbitals are formed by the combination of atomic orbitals when atoms bond together. They can be classified into two types: bonding molecular orbitals and antibonding molecular orbitals.

2. **Bonding Molecular Orbitals**:
- Bonding molecular orbitals are formed when atomic orbitals combine in a way that their wave functions reinforce each other. This leads to an increase in electron density between the nuclei of the bonded atoms, which stabilizes the molecule.

3. **Antibonding Molecular Orbitals**:
- Antibonding molecular orbitals are formed when atomic orbitals combine in a way that their wave functions interfere destructively. This results in a decrease in electron density between the nuclei, which destabilizes the molecule.

4. **Bond Order Calculation**:
- The stability of a molecule can be quantified using the bond order, which is calculated using the formula:
\[ \text{Bond Order} = \frac{(\text{Number of electrons in bonding orbitals}) - (\text{Number of electrons in antibonding orbitals})}{2} \]
- A higher bond order indicates a stronger bond and thus a more stable molecule.

5. **Effect of Bond Order on Stability**:
- When electrons occupy bonding molecular orbitals, the bond order increases. An increase in bond order leads to an increase in bond strength, which in turn stabilizes the molecule.

### Conclusion:
- Therefore, bonding molecular orbitals are the types of orbitals that stabilize a molecule. The presence of electrons in these orbitals increases the bond order and bond strength, contributing to the overall stability of the molecule.