(physics, chemistry) A method of determining the structure of a molecule by assuming that electrons are not fixed to bonds between individual atoms

In theoretical chemistry, an antibonding orbital is a type of molecular orbital that weakens the chemical bond between two atoms and helps to raise the energy of the molecule relative to the separated atoms.

A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals method in particular.

In chemistry, frontier molecular orbital theory is an application of molecular orbital theory describing HOMO–LUMO interactions.