  In this study, we explore the effects of the nucleon's intrinsic
electromagnetic (EM) structure on the nuclear charge radius within the
framework of relativistic continuum Hartree-Bogoliubov (RCHB) theory. By
considering both the EM structure contributions and pairing correlation
effects, we conduct comprehensive calculations, focusing on the plumbum
isotopic chain as an illustrative example. Incorporating both the intrinsic EM
structure corrections and pairing correlation effects leads to a notable
enhancement in the descriptions of mean-square charge radii for even-even Pb
isotopes, as predicted by the RCHB calculations. Furthermore, we identify that
the improvement in charge radii can be primarily attributed to the intrinsic
neutron and neutron spin-orbit terms of the EM structure. On the other hand,
the pairing correlation exerts a more pronounced influence on the isotope
shift, evident in the differential mean-square charge radii. Specifically,
among the EM structure corrections, the pairing correlation predominantly
affects the neutron spin-orbit contribution. In addition to the charge radii
results, we also discuss the nuclear charge densities of Pb isotopes, exploring
their isotopic evolution as captured by the RCHB calculations. This
comprehensive investigation sheds light on the interplay between intrinsic EM
structure and pairing correlations, providing valuable insights into the
nuclear charge distribution and its evolution along the plumbum isotopic chain.
