Spin of Subatomic Particles

Every particle and every atom or molecule (combination of atoms) with a specific energy has its own unique spin. Thus spin is a way of classifying particles. Using spin, all particles that make up matter are fermions. For example, all quarks and leptons have spins of one-half h-bar. The particles which mediate, or convey, the fundamental forces are bosons with spins of one hbar. Baryons are particles made of combinations of three quarks. They have spins of one-half h-bar or three-halves h-bar. Baryons include protons (spin one-half h-bar) and neutrons (spin one-half h-bar). Mesons are particles made of a quark and an antiquark. They have spins of zero h-bar or one h-bar.