We describe an undergraduate laboratory experiment developed for sophomore modern physics students, using the x‐ray analysis feature of a scanning electron microscope. The experiment described is a fundamental physics measurement performed with a state‐of‐the‐art apparatus not usually used in pedagogical physics experiments. The characteristic x‐ray spectrum of elements shows a simple progression that can be quantitatively explained by the conceptually important Bohr–Rutherford shell model of atomic structure. Students measure theKα andKβ x‐ray spectra from metals in the range of 12≤Z≤41. The measurements allow the verification of Moseley’s law scaling of x‐ray energies with atomic number and a quantitative measure of the data’s fit to the shell model.