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
Mole (unit) 1%. The name "mole" is an 1897 translation of the German unit "Mol", coined by the chemist Wilhelm Ostwald in 1894 from the German word "Molekül" (molecule). However, the related concept of equivalent mass had been in use at least a century earlier. The mole was made the seventh SI base unit in 1971 by the 14th CGPM. At the 26th CGPM the definition of the mole was changed from a number derived from a weight (the number of atoms in 12 grams of carbon-12, C) to directly being equal to Avogadro's constant. Since its adoption into the International System