1. The problem statement, all variables and given/known data A hydrogen atom is in a state with energy -0.278 eV. 2. Relevant equations L = nh' 3. The attempt at a solution The answer book says to do E_n = (-13.6 eV)/n^2 but I can't find this equation in our book. Is the 13.6 a significant number or just a different number they used for a different problem? I know I can do this all by myself when I have time to study, but I just want to get this homework done quickly tonight to get it out of the way, since I also have a math quiz tomorrow. I promise I'm usually a good student. I'd appreciate any quick help, thanks!