1. The problem statement, all variables and given/known data The energy required to ionize a helium atom is 24.6 eV. The energy required to remove both the electrons from He atom would be? 3. The attempt at a solution My textbook says- IP1= 24.6 eV IP 2= IP1*Z2 How can they relate the first ionization energy to the second one? The Bohr's atom can be used only for Hydrogen like species and He atom is not Hydrogen like, only it's ion is. How did they relate it?