Topic summary
Quarks
Extracted from the Wikipedia article Quark.
Electric charge
Quarks have fractional electric charge values, either −1/3, or +2/3 times the elementary charge (e), depending on flavor. Up, charm, and top quarks (collectively referred to as up-type quarks) have a charge of +2/3 e; down, strange, and bottom quarks (down-type quarks) have a charge of −1/3 e. Antiquarks have the opposite charge to their corresponding quarks; up-type antiquarks have charges of −2/3 e and down-type antiquarks have charges of +1/3 e. Since the electric charge of a hadron is the sum of the charges of the constituent quarks, all hadrons have integer charges: the combination of three quarks (baryons), three antiquarks (antibaryons), or a quark and an antiquark (mesons) always results in integer charges. For example, the hadron constituents of atomic nuclei, neutrons and protons, have charges of 0 e and +1 e, respectively; the neutron is composed of two down quarks and one up quark, and the proton of two up quarks and one down quark.