These questions are designed to be considered by groups of...

These questions are designed to be considered by groups of students in class. Often these questions work well for introducing a particular topic in class. Explain the difference between the $\sigma$ and $\pi$ MOs for homonuclear diatomic molecules. How are bonding orbitals and antibonding orbitals different? Why are there two $\pi$ MOs and one $\sigma$ MO? Why are the $\pi$ MOs degenerate?

These questions are designed to be considered by groups of students in class. Often these questions work well for introducing a particular topic in class.
Explain the difference between the $\sigma$ and $\pi$ MOs for homonuclear diatomic molecules. How are bonding orbitals and antibonding orbitals different? Why are there two $\pi$ MOs and one $\sigma$ MO? Why are the $\pi$ MOs degenerate?

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Key Concepts

Molecular Orbital Theory

This theory describes how atomic orbitals combine to form molecular orbitals that are spread over a molecule. It explains the electronic structure and properties of molecules by considering the constructive and destructive interference of atomic wave functions.

Sigma and Pi Molecular Orbitals

Sigma (?) orbitals are formed by end-to-end (axial) overlap of atomic orbitals, resulting in electron density concentrated along the internuclear axis. In contrast, pi (?) orbitals are formed by the side-to-side overlap of atomic orbitals, leading to electron density above and below the internuclear axis.

Bonding and Antibonding Orbitals

Bonding orbitals are created by constructive interference between atomic orbitals, which increases electron density between nuclei and stabilizes the molecule. Antibonding orbitals, on the other hand, result from destructive interference, creating a node between nuclei that decreases electron density and destabilizes the molecule.

Degeneracy of Pi Orbitals

The two ? molecular orbitals formed in diatomic molecules are degenerate, meaning they have the same energy, because they arise from the overlap of orbitals oriented in two perpendicular directions that are symmetrically equivalent around the internuclear axis.

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