Editing Quark (section)

=== Electric charge ===
{{See also|Electric charge}}
Quarks have [[fraction (mathematics)|fractional]] electric charge values – either &minus;{{sfrac|1|3}} or +{{sfrac|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 +{{sfrac|2|3}}&nbsp;''e''; down, strange, and bottom quarks (''down-type quarks'') have a charge of −{{sfrac|1|3}}&nbsp;''e''. Antiquarks have the opposite charge to their corresponding quarks; up-type antiquarks have charges of −{{sfrac|2|3}}&nbsp;''e'' and down-type antiquarks have charges of +{{sfrac|1|3}}&nbsp;''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.<ref>
{{cite book
 |author=C. Quigg
 |chapter=Particles and the Standard Model
 |editor=G. Fraser
 |title=The New Physics for the Twenty-First Century
 |page=91
 |publisher=[[Cambridge University Press]]
 |year=2006
 |isbn=978-0-521-81600-7
}}</ref> For example, the hadron constituents of atomic nuclei, neutrons and protons, have charges of 0&nbsp;''e'' and +1&nbsp;''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.<ref name="Knowing" />