Elementaarlaengut

Elementaarlaengut, or the elementary charge, is a fundamental physical quantity representing the smallest unit of electric charge observed in nature. It is the charge carried by elementary particles such as the electron (−e) and the proton (+e). The magnitude of the elementary charge is quantized: any observable charge is an integer multiple of e.

In the International System of Units (SI), the elementary charge is fixed as an exact value: e = 1.602176634 × 10^−19 coulombs. Since the 2019 redefinition of the SI, the coulomb is a derived unit defined via the fixed value of e and the second, with the ampere defined by fixing e as the elementary charge per unit of current. This makes e an exact constant in nature.

Quarks carry fractional charges, ±e/3 or ±2e/3, but they do not exist freely due to confinement within hadrons. Consequently, ordinary matter exhibits charges in integer multiples of e, while the fundamental constituents may carry fractional charges.

The elementary charge is a central constant in physics, governing electromagnetic interactions. It appears in Coulomb’s law and in quantum electrodynamics, and it determines the strength of the electromagnetic coupling through the fine-structure constant α. The value of e is known with extraordinary precision and is a standard reference in experiments and calculations across physics, chemistry, and engineering, with CODATA providing the recommended value.