My theory is the space is charged fluid. All things are within it. Positive charged nucleus attract the negative charged fluid to form atoms. The density of the fluid is Df=1/r^3. Electrons also attracted by positive charged nucleus and stable at atom radius where the attracting force is equal to the repel force. A demo The electrons around the atom is like bond by a spring, need force to push in or pull out from the nucleus. Now if a force is applied, the electron will vibrating and produce pressure/EM wave across the space around it. Every element has certain charge and bonding strength, therefore unique spectrum. If Coulombs's law stands universally, we should assume that every atom or charged particle are connected by their force field across the whole space. An atoms force field does not end at atom radius, but extend to infinity. In whole, an atom or planet maybe electrically neutral, but Every charge within has its own force field beyond distance, those forces overlapped to produce chemical bonding, magnetism and gravity. If proton is in fact built by U and D quarks, then maybe the proton is like one small woman sleep between two fat man. It happens in real life. At least, the 3 quarks could electrically form into a group that we called proton. We should assume all nucleus have some degree of polarity according their unique charges carried and the structure of all quarks stick together. An iron atom maybe is a small magnet, the positive pole of the nucleus attract dense space fluid to form a force field that its density/strength drop off at 1/r^3, that matches the observation, and fits Coulombs law.