1. The problem statement, all variables and given/known data Find the expectation value for a hydrogen atom's radius if n=25 and l=0. 2. Relevant equations expectation value = <f|o|f> where f=wavefunction and o=operator 3. The attempt at a solution So I know that to find an expectation value, you integrate over all relevant space: (f*)(o)(f)... However I'm not sure what "f" is in this case... my book only lists hydrogen atom wavefunctions up through like n=3, but nothing past it... also what would be the operator that relates to radius?? In class I think we derived something for the H atom that shows that its wavelength has a radial and an angular part but I'm entirely confused Also, what's the difference when the question is stated like above and when it says to find the mean radius <r> of H in a certain orbital? Isn't it pretty much the same thing?