Credit: (Courtesy: Washington University in St. Louis)
This graph basically shows where the protons are (more solid lines exp and ch ) and where the neutrons are (dotted lines n and w) in the nucleus — and the neutrons are located in the thick skin, where the dotted lines separate from the solids. To be precise, the experimental (maroon staggered line) and fitted (black) charge distribution are the solids, neutron matter distribution (blue) and the weak charge distribution (red hashes) are the dotted lines.