Editing Elementary charge (section)

=== Quantum of charge ===
All known [[elementary particle]]s, including quarks, have charges that are integer multiples of {{sfrac|1|3}}&nbsp;''e''. Therefore, the "[[quantum]] of charge" is {{sfrac|1|3}}&nbsp;''e''. In this case, one says that the "elementary charge" is three times as large as the "quantum of charge".

On the other hand, all ''isolatable'' particles have charges that are integer multiples of ''e''. (Quarks cannot be isolated: they exist only in collective states like protons that have total charges that are integer multiples of ''e''.) Therefore, the "quantum of charge" is ''e'', with the proviso that quarks are not to be included. In this case, "elementary charge" would be synonymous with the "quantum of charge".

In fact, both terminologies are used.<ref>''Q is for Quantum'', by John R. Gribbin, Mary Gribbin, Jonathan Gribbin, page 296, [https://books.google.com/books?id=zBsDkgI1uQsC&pg=RA1-PA296 Web link]</ref> For this reason, phrases like "the quantum of charge" or "the indivisible unit of charge" can be ambiguous unless further specification is given. On the other hand, the term "elementary charge" is unambiguous: it refers to a quantity of charge equal to that of a proton.