nonbonding

Nonbonding is a term used in chemistry to describe electrons or orbitals that do not participate in chemical bonding between atoms. It is used in valence bond theory to describe lone electron pairs on atoms, and in molecular orbital theory to describe orbitals that do not contribute to bond formation. Nonbonding interactions, such as van der Waals forces and hydrogen bonds, are noncovalent and influence molecular assembly.

Lone pairs are the most common nonbonding electrons; they occupy nonbonding orbitals with higher energy and are localized on a single atom. These lone pairs influence molecular geometry through repulsion with bonding pairs (VSEPR). For example, the water molecule has two lone pairs on oxygen; these reduce the HOH angle to about 104.5 degrees.

In molecular orbital theory, nonbonding orbitals are molecular orbitals with little or no net overlap between the participating atoms; they are often localized on one atom and may originate from p or lone-pair atomic orbitals. They can remain largely nonbonding in many molecules, contributing to properties such as electron density distribution.

Nonbonding interactions arise from nonbonding electron distributions and are typically weaker than covalent bonds. They include London dispersion forces, dipole-induced dipole interactions, and hydrogen bonding, the latter involving lone pairs on electronegative atoms as electron-pair donors.