b marks 5. (a) Describe the key experimental evidence that indicates there are discrete energy levels in atoms. (b) Consider the energy levels of a helium atom that is (i) neutral, or (ii) singly-ionised helium atom (i.e. with one electron removed) In each case, would you expect the energy levels of the helium atom to be the same, similar or very different to a neutral hydrogen atom? Explain your reasoning