Ok, so the question is: A metal has a threshold wavelength for the onset of the photoelectric effect of 662 nm. What is the binding energy (kj/mol) of an electron to the metal surface. I used E=hv to get the photon energy, so is that the binding energy as well? If so, how do i convert it to kJ/mol, do i use avagadro's number? Any help is appreciated, thanks!