protons and neutrons
Particles that are composed of three quarks are called baryons . The two best known baryons are protons and neutrons. A proton is composed of two up quarks and one down quark uud . The charge on the proton is the result of adding the charges on these quarks . Neutrons are composed of one up quark and two down quarks udd . The charge on the neutron is the result of adding the charges on these quarks .