Using the arguments of this section, can you give a reasonable explanation why the elements F and Cl are gases, that is, why a molecule of two F or Cl atoms would be very weakly bound? In particular, without knowing details of the molecular states, why would you expect F₂ to have about half the binding energy of O₂? (The actual ratio is about one-third).

It would seem that in the LCAO approximation there is no reason for noble gases like Ne and Ar to ever form molecules or solids. Solids of these materials are possible, however. They are bound by the much weaker van der Waals force.