Every time I try to understand how forces which hold atoms and molecules together work, I find myself wanting to ask this question: why not the other way around? Could there be an atom which has electrons and neutrons inside, and protons outside?
It feels like a silly question, but is there something we know about the universe we live in that implies that this is not possible?
Electrons are not subject to the strong nuclear force that glues the protons neutrons together. This means that no attractive force would prevent electric repulsion to scatter a “electron nucleus”.
From a field theory perspective, the strong nuclear force is a SU(3) gauge interaction and the electron field transforms as a singlet under that SU(3)
This was my thoughts to. Electrons don’t clump together on their own. Do gluons even affect electrons at all, or is that more of a baryonic thing?
Strong interaction is really designed as a baryonic thing, leptons have no color charge (which is another way to say that they transform as SU(3) singlets). Leptons do not interact with gluons.
Not at tree-level anyway. See for example this list of vertices.
At loop levels, it’s possible to imagine an electron decaying into neutrino+W, then W into two quarks who can then interact with gluons, but as it’s down a couple of orders in perturbation theory so probably much too weak to hold a nucleus together. Not an expert in particle physics so I do not know with certainty whether a couple-of-loops interaction can have a measurable effect.