Consider a two-electron atom in which the electrons, orbiting a nucleus of charge +Ze, follow Bohr-like orbits of the same radius r, with the electrons always on opposite sides of the nucleus.
(a) Show that the net force on each electron is toward the nucleus and has magnitude The energy needed to remove both electrons is just the negative of the energy you found in part.
(d). Compute the energy needed to remove both electrons in helium, and then repeat for Li+. Compare your results with the experimental values of 79.0 eV and 198 eV, respectively.