1. (a) State the equation for the electrical force between a nucleus of charge Q and an electron of charge e , and mass m , about which it orbits at a radius r .
2. (b) Show that the kinetic energy of the electron is EK=2rkQe .
3. (c) Show that the total energy of the electron in its orbit around the nucleus is less than zero.
4. (d) The total energy of an electron in its ground state in a hydrogen atom is −13.6 eV . Calculate the radius of the electron's orbit around the nucleus.