Proved that neutrons. Mesner is both a physicist and a chemist. He used physics and chemistry to design experiments. He bombarded beryllium with alpha particles, and then bombarded hydrogen and nitrogen with rays produced by beryllium. As a result, hydrogen nuclei and nitrogen nuclei are produced. This can only be explained by assuming that the rays emitted by beryllium are neutral particles with the same mass as protons. Because these particles are uncharged, they are called neutrons, so they are called pioneers of nuclear science.