It is clear that some modes of resonance would make larger contributions (be more mechanically stable than others), and that in particular asimple ratio of number of bonds to number of positions would be exceptional.
Puling je preučeval tudi lastnosti medatomskih sil v kovinah in ugotovil, da je v kemijske vezi vključena približno polovica od petih d-orbital prehodnih kovin, preostale nevezne d-orbitale pa določajo magnetne lastnosti.