elementary charge

https://dx.doi.org/10.1351/goldbook.E02032
Electromagnetic fundamental physical constant equal to the charge of a proton and used as atomic unit of charge Math - ei.
See also: electric charge
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 972