1. The problem statement, all variables and given/known data a) Explain qualitatively why the energy required to remove one electron from the ground state of the helium atom is much larger than that in hydrogen, while for other states the hydrogenic value is quite a good approximation, e.g. the 1s2s levels in helium have energies very similar to the 2s energy in hydrogen. b) The 1s2s conﬁguration in helium is split into two levels. Explain brieﬂy the physical origin of the splitting, and how it comes about that these diﬀerent energies should be associated with diﬀerent relative orientations of the intrinsic spins of the two electrons (so that one of the levels is called a “singlet”, and the other a “triplet”). 2. Relevant equations none 3. The attempt at a solution a) The ground state of helium has direct exposure to a greater charged nucleus than hydrogen so the ionisation energy is greater. The other levels of helium are shielded by previous levels' electrons. b) no idea.