Every atomic nucleus contains one or more protons.
The mass of the proton is 1,836 times the mass of the electron and slightly less than the mass of the neutron . Protons are no longer considered elementary particles, but are made up of smaller particles called quarks . In 1919 Ernest Rutherford discovered the proton as a product of the disintegration of the atomic nucleus . The antiproton, the proton's antiparticle , was discovered in 1955. When found in the nucleus of an atom, protons and neutrons are called nucleons .