electron

Elementary particle not affected by the strong force having a spin quantum number 1 2, a negative elementary charge and a rest mass of 0.000 548 579 903 13 u.
Source:
Green Book, 2nd ed., p. 93
See also:
PAC, 1982, 54, 1533 (Glossary of terms used in nuclear analytical chemistry (Provisional)) on page 1540