Protons are positively electric; electrons negative. This is an attractive situation. Where do the shells come from that keep electrons from falling into the protons under attraction?
The answer can be addressed by many ways. Here is some, which follows from AWT
: the rotating electron makes the vacuum foam near protons so dense by shaking, it will become flowing on the surface of the resulting dense blob of vacuum like bubble at the water droplet surface.
The another answer can follow from the description of electron orbital like the mercury droplet separating the electron from photon by surface tension. The breakthrough of the surface membrane by electron would require the temporal formation of strongly negatively curved surface with negative, repulsing potential, which is not possible.
By another words, this absence of electron fall into atom nuclei can be explained as a sort of buoyancy or surface tension phenomena. We can even invent the explanation based on the laws of optics of electron wave spreading and total reflection phenomena and many others, but all these explanation will remain inertia and Newtonian mechanics based.
It should be noted, inside the neutron stars the electron can be pushed into proton under formation of neutron due the strong repulsive force of another electrons. The same phenomena will occur, if you place the electron and proton into dense vacuum near the black hole. The density of vacuum will compensate the density of field near the particles by such way, these particles will condense nearly seamlessly into neutron or even heavier particle. From the same reason the resulting neutron will decompose easily into neutrino and gamma radiation, though.