Editing Molecular orbital (section)

====He<sub>2</sub>====
On the other hand, consider the hypothetical molecule of He<sub>2</sub> with the atoms labeled He' and He". As with H<sub>2</sub>, the lowest energy atomic orbitals are the 1s' and 1s", and do not transform according to the symmetries of the molecule, while the symmetry adapted atomic orbitals do. The symmetric combination—the bonding orbital—is lower in energy than the basis orbitals, and the antisymmetric combination—the antibonding orbital—is higher. Unlike H<sub>2</sub>, with two valence electrons, He<sub>2</sub> has four in its neutral ground state. Two electrons fill the lower-energy bonding orbital, σ<sub>g</sub>(1s), while the remaining two fill the higher-energy antibonding orbital, σ<sub>u</sub>*(1s). Thus, the resulting electron density around the molecule does not support the formation of a bond between the two atoms; without a stable bond holding the atoms together, the molecule would not be expected to exist. Another way of looking at it is that there are two bonding electrons and two antibonding electrons; therefore, the bond order is 0 and no bond exists (the molecule has one bound state supported by the Van der Waals potential).{{citation needed|date=January 2014}}