James Chadwick’s experiment was conducted in 1932 to determine the mass of the neutron. He bombarded beryllium with alpha particles (the nuclei of helium atoms) and detected the presence of radiation that had a mass of about one-third of the mass of a hydrogen atom. This radiation was identified as a neutral particle, which he named the neutron. He was able to calculate the mass of the neutron by measuring the energy of the alpha particles that collided with the beryllium and the energy of the neutron radiation that was released. His experiment established the neutron as an essential part of the atomic nucleus and provided the basis for the development of nuclear energy. Chadwick was awarded the Nobel Prize in Physics in 1935 for his discovery of the neutron.
