Consider a hydrogen like atom whose energy in ${n^{{\rm{th}}}}$ excited state is given by ${E_n} = - \frac{{13.6\,\,{Z^2}}}{{{n^2}}}$ . When this excited atom makes a transition from excited state to ground state, most energetic photons have energy ${E_{\max }} = 52.224\,\,eV$ and least energetic photons have energy ${E_{\min }} = 1.224\,\,eV$. The atomic number of atom is