Consider a sample of hydrogen like atom in n^th excited state .When these excited atoms make a transition to ground state, the most energetic photons have energy  ${\text{E}}_{\text{max}}=\text{51 eV}$ and the least energetic photons have energy  ${\text{E}}_{\text{min}}=\text{2}.\text{6 eV}$. The atomic number of atom is z. find the value of  $\text{z}+\text{n}$.