1. The problem statement, all variables and given/known data An absorption line at 6966 eV is known to come from a hydrogen-like ion. Calculate the likely atomic number of the element and hence identify it. (The ionization energy of hydrogen is 13.6eV.) 2. Relevant equations not sure 3. The attempt at a solution Using E=(13.6Z^2)/n^2 eV where n=1 => 6966=13.6Z^2 So Z=22.6. I thought I should get a precise whole number and neither Z=22or 23 are hydrogen-like ions, so I think I must have done this wrong.