Calculate the potential energy of interaction between the two electrons in the helium atom when they are separated by a distance of 1 Å. Similarly, what would be the potential energy of one of these electrons if it were alone in the presence of the He nucleus at a distance 1 Å? How would you combine these two results to obtain an estimate of the first ionization energy of He? Estimate the 2nd ionization energy of He by considering the distance of its electrons from the nucleus to be 1 Å.