Assertion: electron | /r/HasProperty | 0.511 mev/c2
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Source sentences:
text: When Rosenfeld named them, the only known leptons were electrons and muons, whose masses are indeed small compared to nucleons—the mass of an electron (0.511 MeV/c2) and the mass of a muon (with a value of 105.7 MeV/c2) are fractions of the mass of the "heavy" proton (938.3 MeV/c2).