The ground state for a single valence electron of a rubidium atom (Z=37) is 5s and its energy is –4.18 eV. The valence electron is excited into the 5g state. We want to determine the energy of this 5g electron. Assume that the wave function for this 5g electron places it entirely outside the electron cloud of the 36 other electrons in the atom. These 36 electrons effectively "shield" 36 of the nuclear protons from interaction with the 5g electron. Write the equation relating the approximate energy of such a "screened" system to the effective number of "unscreened" protons in the nucleus and the principle quantum number of the 5g electron.