The quantization of energy states of neon and argon are measured and analyzed in the Franck-Hertz experiment. The results of the Franck-Hertz experiment is consistent with the Bohr model. The main idea of the Franck-Hertz experiment is that the Franck-Hertz curves are linearly increasing curves but their minimas are not equally spaced due to the mean free path dependence. And this idea that an atom occupies one of the atom’s ”quantum energy levels” is consistent with Niel Bohr’s model. Our experiment precisely illustrates the key concept of the Franck-Hertz Experiment. We found the discrete energy levels of neon to occur at \(19.4993\pm 0.6\) eV; whereas, for argon it occurs at \(10.7991\pm 0.02\) eV.