Electron pair

In chemistry, an electron pair or Lewis pair consists of two electrons that occupy the same molecular orbital but have opposite spins.

Gilbert N. Lewis introduced the concepts of both the electron pair and the covalent bond in a landmark paper he published in 1916.

[1][2] Because electrons are fermions, the Pauli exclusion principle forbids these particles from having all the same quantum numbers.

They can form a chemical bond between two atoms, or they can occur as a lone pair of valence electrons.

In the case of metallic bonding, the magnetic moments also compensate to a large extent, but the bonding is more communal, so that individual pairs of electrons cannot be distinguished and it is better to consider the electrons as a collective 'sea'.

MO diagrams depicting covalent (left) and polar covalent (right) bonding in a diatomic molecule . In both cases a bond is created by the formation of an electron pair.