This creates an electrostatic potential energy. Intermolecular energy is the energy due to neighboring molecules. If we go back to our system that's composed of two diatomic oxygen molecules, we see that the protons found on this nucleus will attract the electrons of the neighboring atom. And the same thing for this one. The proton here will attract electrons here, and they will create potential energy, okay? Now, to find an internal energy of the system, I would literally have to look at every single one of these for this molecule.