[en] The nature of the anomalous kink observed in the isotope shifts of the rms charge radii of lead nuclei is analyzed. First, an analytical fit to the experimental data on the mean square charge radius and to QCD-calculation of the neutron charge distribution is given, and is used to recognize the neutron charge distribution when calculating the charge density distribution in a finite nucleus. Relativistic Thomas-Fermi calculations, with and without density-dependent coupling constants, are performed, and the effect of the neutron charge distribution on the lead isotopes shifts is discussed. Secondly, the electromagnetic component of the self-energy is modified to notify the Coulomb force between charges and the effect on lead isotopes shifts is studied. Finally, the wave mechanical nature of the anomaly in the charge radii of lead isotopes is proved by comparing the results of relativistic mean-field theory with the results of its semiclassical approximations implying the same parameter set. Semiclassical treatments reproduce the average shift in the rms charge radii of lead isotopes, but not the anomalous kink. (author)