Due to the atomic pairwise nature of the structural bonding, we can draw molecules as graphs (that The accumulation of electronic density as a bonding pattern, beyond its ubiquitousness, has a second advantage: it is an observable property (as in quantum mechanically observable ). Opposed to the esoteric orbitals and wave functions, it can be experimentally checked (even if it is technically challenging, see Fig. ). And contrary to the energy perspective of the bond, it is a phenomenon that can be observed inside the bond, directly between the involved atoms (although it was argued that bonding is not a submolecular phenomenon ).