Protons, neutrons, and electrons each have different masses. Electrons are, by far, the lightest of the three, with a mass of only about 1/2000th that of a proton or neutron. Protons and neutrons have similar masses, with that of the neutron being just slightly higher than that of the proton. The masses of the three particles in kilograms are:

Electron mass: 9.1094 × 10⁻³¹ kg

Proton mass: 1.6726 × 10⁻²⁷ kg

Neutron mass: 1.6749 × 10⁻²⁷ kg

Nuclear decay processes can involve the release of electrons, protons, neutrons, or combinations of these basic particles.