text: Well for one thing it explains why electrons don't spiral into the nucleus (as classical physics would predict). \n\nQuantum mechanical theory states that electrons will inhabit discrete energy levels (orbitals). Therefore it would only fall into the nucleus if it lost exactly the right amount of energy, but there is a limit to the energy values it can emit in the form of a photon. \n\nThe main point is that available energy values are not continuous and this why electrons fall into strictly defined orbits rather than just going anywhere they want to or colliding with the nucleus.