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'''Protons''' are one of the two types of [[sub-atomic]] particles that form in the [[nucleus]] of an [[atom]] (together with [[neutron]]s).<ref>Serway, Beichner: ''Physics for Scientists and Engineers'', 5th edition</ref>

'''Protons''' are one of the two types of [[sub-atomic particles]] that form in the [[nucleus]] of an [[atom]] (together with [[neutron]]s).<ref>Serway, Beichner: ''Physics for Scientists and Engineers'', 5th edition</ref>

A proton is made up of two up [[quark]]s and one down quark.  According to the [[Standard Model]] of particle physics, quarks are [[fundamental particle]]s, meaning that they cannot be split into smaller particles.<ref>Krane: ''Modern Physics'', 2nd edition</ref>

A proton is made up of two up [[quark]]s and one down quark.  According to the [[Standard Model]] of particle physics, quarks are [[fundamental particles]], meaning that they cannot be split into smaller particles.<ref>Krane: ''Modern Physics'', 2nd edition</ref>

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