Remember that our goal is to understand digital electronics. Macroscopic separations of positive and negative charges are energetically unfavorable. Neutron has almost same mass as proton, slightly larger. Big, fluffy cotton ball with tiny, but heavy, steel BB at center 1 mm BB at 50 yd.
Light is emitted when atom relaxes to ground state from excited state.
On careful examination, find that light emitted by excited atoms has discrete values of energy. Deduce that electrons in an atom have discrete values of energy. Energy levels of electrons in an atom are quantized.