Construct the molecular orbital diagram for H2 and then identify the bond order. 1S Bond order
The Correct Answer and Explanation is :
The molecular orbital (MO) diagram for the hydrogen molecule (H₂) can be constructed by considering the atomic orbitals of the two hydrogen atoms and how they combine to form molecular orbitals. In this case, hydrogen atoms each have a 1s atomic orbital.
Steps to Construct the MO Diagram for H₂:
- Atomic Orbitals (AO):
Each hydrogen atom has a 1s atomic orbital. These atomic orbitals will combine to form molecular orbitals. - Combination of Orbitals:
When two atomic orbitals overlap, they form two molecular orbitals:
- Bonding Molecular Orbital (σ₁s): This is formed when the atomic orbitals combine constructively, resulting in electron density between the two nuclei.
- Antibonding Molecular Orbital (σ*₁s): This is formed when the atomic orbitals combine destructively, creating a region of reduced electron density between the nuclei, leading to an antibonding interaction.
- Energy Level Arrangement:
- The bonding molecular orbital (σ₁s) is lower in energy than the atomic orbitals.
- The antibonding molecular orbital (σ*₁s) is higher in energy than the atomic orbitals.
- Electron Filling:
- Each hydrogen atom has one electron, so in H₂, there are two electrons to place in the molecular orbitals.
- The two electrons will occupy the lower energy bonding molecular orbital (σ₁s).
Bond Order Calculation:
Bond order is calculated using the formula:
[
\text{Bond Order} = \frac{1}{2} \left( \text{Number of electrons in bonding MOs} – \text{Number of electrons in antibonding MOs} \right)
]
For H₂:
- There are 2 electrons in the bonding molecular orbital (σ₁s).
- There are 0 electrons in the antibonding molecular orbital (σ*₁s).
Thus, the bond order is:
[
\text{Bond Order} = \frac{1}{2} (2 – 0) = 1
]
Explanation:
The bond order of 1 indicates that the H₂ molecule has a single bond between the two hydrogen atoms. This is consistent with the fact that H₂ forms a stable molecule with a single covalent bond between its atoms. The presence of two electrons in the bonding molecular orbital contributes to the attraction between the nuclei, leading to a stable bond. The antibonding orbital is empty in the ground state of the molecule, so it does not affect the bond strength. Therefore, the bond order of 1 is indicative of a single, stable covalent bond in the H₂ molecule.