A proton is a stable subatomic particle, symbol p, H+, or 1H+ with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than the mass of a neutron and 1,836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei).
Ernest Rutherford at the first Solvay Conference, 1911
The neutron is a subatomic particle, symbol n or n0, which has a neutral charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, they are both referred to as nucleons. Nucleons have a mass of approximately one atomic mass unit, or dalton. Their properties and interactions are described by nuclear physics. Protons and neutrons are not elementary particles; each is composed of three quarks.
Institut Laue–Langevin (ILL) in Grenoble, France – a major neutron research facility
Cold neutron source providing neutrons at about the temperature of liquid hydrogen