Main Page | See live article | Alphabetical index The becquerel (abbreviation Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. It is therefore equivalent to s-1. The older unit of radioactivity was the curie (Ci). 1 Bq = 2.7×10-11 Ci. It was named after Henri Becquerel, who shared a Nobel Prize with Marie Curie for their work in discovering radioactivity. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.