1. Write an expression for the energy of a single electron in a hydrogen-like orbit. Your expression should take into account a nuclear charge of Z and quantum number n. (b) Express your answer in Hartrees if the electron is in a hydrogen 1s orbital. (c) Calculate the energy in Hartrees of an electron in a helium 1s and a helium 2s orbital, neglecting the electron-electron repulsion term in the Hamiltonian.