The physicist known for the discovery of the neutron is James Chadwick. In 1932, Chadwick conducted experiments that led to the identification of the neutron, a previously unknown subatomic particle. His discovery was significant as it contributed to the understanding of atomic structure and the development of nuclear physics. The neutron's existence is crucial for explaining nuclear reactions and the behavior of atoms. Chadwick's work earned him the Nobel Prize in Physics in 1935, solidifying his legacy in the scientific community and paving the way for advancements in both energy and medicine.