1. With q being the elementary charge and n the electron density. 2. The elementary charge , measured in terms of the Planck charge, is 3. This elementary charge is a fundamental physical constant. 4. The electron is a stable particle possessing one elementary charge and one electron mass. 5. "The ampere is equivalent to one coulomb ( roughly times the elementary charge ) per second. 6. In this case, " elementary charge " would be synonymous with the " quantum of charge ". 7. Na + is a sodium ion with charge number positive one ( an electric charge of one elementary charge ). 8. The elementary charge is one of the fundamental physical constants, and accurate knowledge of its value is of great importance. 9. For instance, the accepted value of the unit of elementary charge can properly be expressed as, which is shorthand for 10. The magnitude of the elementary charge was first measured in Robert A . Millikan's noted oil drop experiment in 1909.