Which of the following would you expect to be more favorable...

Which of the following would you expect to be more favorable energetically? Explain.
a. an $\mathrm{H}_{2}$ molecule in which enough energy is added to excite one electron from the bonding to the antibonding $\mathrm{MO}$
b. two separate $\mathrm{H}$ atoms

Key Concepts

Molecular Orbital Theory

This theory explains that electrons in molecules occupy orbitals that extend over the entire molecule. It distinguishes between bonding orbitals, which lower the energy of the molecule when occupied, and antibonding orbitals, which raise its energy. Understanding how electrons fill these orbitals is crucial for predicting molecular stability.

Bond Order

Bond order is calculated by taking the difference between the number of electrons in bonding and antibonding orbitals, divided by two. A higher bond order indicates a stronger and more stable bond, whereas a reduced bond order (such as when electrons occupy higher-energy antibonding orbitals) leads to decreased stability.

Electronic Excitation

Electronic excitation involves promoting an electron from a lower-energy orbital to a higher-energy orbital. In the context of molecular systems, exciting an electron from a bonding orbital to an antibonding orbital disrupts the favorable interactions that stabilize the molecule, thereby making it less energetically favorable.

Energetic Stability Comparison

When comparing different species, it is important to consider the overall energy after taking into account bonding interactions. Systems with unperturbed favorable bonding interactions are typically lower in energy than those in which such interactions have been compromised by electronic excitation or other perturbations.

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