Valence bond theory describes bonding as a consequence of the overlap of two separate atomic orbitals on different atoms that creates a region with one pair of electrons shared between the two atoms. When they overlap in a fashion that creates a node along this axis, they form a π bond

When the orbitals overlap along an axis containing the nuclei, they form a σ bond. We can use hybrid orbitals, which are mathematical combinations of some or all of the valence atomic orbitals, to describe the electron density around covalently bonded atoms.

valence bond theory — description of bonding that involves atomic orbitals overlapping to form σ or π bonds, within which pairs of electrons are shared. node — plane separating different lobes of orbitals, where the probability of finding an electron is zero. overlap — coexistence of orbitals from two different atoms sharing the same region of space, leading to the formation of a covalent bond. hybridization — model that describes the changes in the atomic orbitals of an atom when it forms a covalent compound.