How did James Chadwick’s discovery of the neutron support Rutherford’s ideas about the nucleus?

James Chadwick’s 1932 discovery of the neutron provided essential support for Ernest Rutherford’s model of the atomic nucleus by resolving a significant discrepancy regarding atomic mass.12

Prior to this discovery, physicists observed that elements heavier than hydrogen possessed an atomic mass greater than their atomic number, or the number of protons present. While some had theorized that additional protons might be shielded by electrons within the nucleus, Chadwick’s identification of a neutral particle with a mass nearly equal to that of a proton offered a more accurate explanation.12

This discovery confirmed that the nucleus is a composite body consisting of both protons and neutrons. By accounting for the "missing" mass, the neutron validated the core concept of Rutherford’s model—that the nucleus is a dense, massive center of the atom—and provided the foundation for the modern understanding of nuclear structure.231