1. The problem statement, all variables and given/known data A hydrogen like system has ionization energy of 11808 kJ/mol. Find the number of protons in the nucleus. 2. Relevant equations Not sure. Should I use the formula En = E1/n2? 3. The attempt at a solution The ionization energy of H is 1312 kJ/mol. The ionization energy of the system is 11808 kJ/mol. Since this is hydrogen like system, it has only one electron in its outer shell and so the effects of electron repulsion can be ruled out. If I try to use the above formula, I am not getting the answer. Or should I use the complicated formula for total energy of the system and then try to find z from it?