The following is part of a molecular orbital energy-level diagram for MOs constructed from 1s atomic orbitals.

(a) What labels do we use for the two MOs shown?

Verified step by step guidance

1. Identify the atomic orbitals involved in the formation of molecular orbitals. In this case, the diagram shows molecular orbitals formed from 1s atomic orbitals.
2. Recognize that the two molecular orbitals formed from 1s atomic orbitals are the bonding and antibonding molecular orbitals.
3. Label the lower energy molecular orbital as the bonding molecular orbital, denoted as σ(1s).
4. Label the higher energy molecular orbital as the antibonding molecular orbital, denoted as σ*(1s).
5. Note that the bonding molecular orbital (σ(1s)) is lower in energy and more stable, while the antibonding molecular orbital (σ*(1s)) is higher in energy and less stable.

Key Concepts

Molecular Orbitals (MOs)

Molecular orbitals are formed by the linear combination of atomic orbitals (LCAO) when atoms bond. In the case of diatomic molecules, the 1s atomic orbitals from each atom combine to create two types of molecular orbitals: bonding and antibonding. The bonding molecular orbital is lower in energy and stabilizes the molecule, while the antibonding molecular orbital is higher in energy and can destabilize it.

Bonding and Antibonding Orbitals

Bonding orbitals are formed when atomic orbitals combine constructively, leading to increased electron density between the nuclei, which stabilizes the molecule. Antibonding orbitals, on the other hand, result from destructive interference, creating a node between the nuclei and leading to decreased electron density in that region, which can destabilize the molecule. The labels for these orbitals are typically denoted as σ (sigma) for bonding and σ* (sigma star) for antibonding.

Energy-Level Diagrams

Energy-level diagrams visually represent the relative energies of molecular orbitals. In these diagrams, bonding orbitals are placed lower in energy than their corresponding antibonding orbitals. The arrangement helps predict the stability of the molecule based on the number of electrons in each type of orbital, guiding the understanding of molecular structure and reactivity.