We know that: The energy of He+ can be calculated as the hydrogen like atom E = - 2p2me4 / n2h2 * Z2 = - 13.6 eV / n2 *Z2 Z = 2 for He atom ; n= 5 given = -13.6 eV / 25 * 4 = - 2.176 eV x1.602 x 10-19 J / eV = 3.48 x 10-19 J = 3.48 x 10-16 kJ Solution We know that: The energy of He+ can be calculated as the hydrogen like atom E = - 2p2me4 / n2h2 * Z2 = - 13.6 eV / n2 *Z2 Z = 2 for He atom ; n= 5 given = -13.6 eV / 25 * 4 = - 2.176 eV x1.602 x 10-19 J / eV = 3.48 x 10-19 J = 3.48 x 10-16 kJ.