Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The Highest Occupied Molecular Orbital (HOMO) is the highest energy orbital containing electrons in a molecule under ground state conditions. It plays a crucial role in determining how a molecule interacts with light and other chemical entities.
Related terms
Lowest Unoccupied Molecular Orbital (LUMO): The LUMO is the lowest energy orbital that does not contain electrons but can accept them during chemical reactions or when absorbing energy.
Photoelectron Spectroscopy: A technique used to measure the ionization energies of molecules, providing information about their HOMOs.
Electronic Transition: A process where electrons move between different molecular orbitals, such as from HOMO to LUMO, often induced by absorbing ultraviolet or visible light