The neutron's existence was theorized by Rutherford in 1920 and discovered by Chadwick in 1932, according to the American Physical Society. Neutrons were found during experiments when atoms were shot at a thin sheet of beryllium. Subatomic particles with no charge were released — the neutron.
Neutrons are uncharged particles found within all atomic nuclei (except for hydrogen). A neutron's mass is slightly larger than that of a proton. Like protons, neutrons are also made of quarks — one "up" quark (with a positive 2/3 charge) and two "down" quarks (each with a negative one-third charge).