Becquerel Becquerel The becquerel (; symbol: Bq) is the SI derived unit of radioactivity. One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The becquerel is therefore equivalent to an inverse second, s. The becquerel is named after Henri Becquerel, who shared a Nobel Prize in Physics with Pierre and Marie Curie in 1903 for their work in discovering radioactivity. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is uppercase (Bq). However, when an SI unit is spelled out
2019 redefinition of SI base units values associated with the following constants of nature: The seven definitions above are rewritten below with the derived units (joule, coulomb, hertz, lumen and watt) expressed in terms of the seven base units (second, metre, kilogram, ampere, kelvin, mole and candela), according to the updated 9th edition of the SI Brochure (2018). In the list that follows, the symbol sr stands for the dimensionless unit steradian. As part of the redefinition, the international prototype kilogram was retired and definitions of the kilogram, the ampere, and the kelvin were replaced. The definition of the mole was revised. These changes have the