To write the electron configuration, you begin with the
normal electron configuration of the element and then add or deduct the number
of electrons that the charge designates. Rubidium will change from
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^1
to
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 because it loses the last
electron.
