The valence bond (VB) theory of bonding was mainly developed by Walter Heitler and Fritz London in 1927, and later modified by Linus Pauling to take bond direction into account. The VB approach concentrates on forming bonds in localized orbitals between pairs of atoms, and hence retains the simple idea of Lewis structures and electron pairs. The wave function for the bonding electrons is described as the overlap of atomic orbitals. Thus, in the H2 molecule, the spherical s orbitals of the two H atoms simply overlap, so that the electrons in the bond sense the nuclei of both atoms. This method also works well for simple molecules like H2O, CH4, and NH3. First the appropriate hybrid orbitals are constructed on the central atom to give the correct molecular geometry (e.g., four sp3 tetrahedral orbitals on the C atom in CH4). The bonding picture is then constructed by simple overlap of the atomic orbitals, (e.g., one 1s orbital of a H atom with each sp3 lobe of the C atom in CH4 to give four C–H bonds).
