Z=1 for hydrogen ; n=2 En=−k(nZ)2E2=4−k×1E2=−328KJmol−1;k=4×328E4=16−k×1E4=−4×328×161E4=−82KJmol−1 Related Theory The total mechanical energy of an electron in a Bohr orbit is the sum of its kinetic and potential energies. The lowest energy is called the ground state. Caution It is given that the energy of the electron in the first Bohr H-atom is −13.6eV