Becquerel and curie

The becquerel (Bq) is one nuclear disintegration per second, the SI unit of activity. The older curie (Ci) is 3.7 × 10^10 Bq, originally defined as the activity of one gram of radium-226. A typical microcurie radioisotope source used in a teaching demonstration is 37 kBq. A radiocarbon-active modern carbon sample sits at about 0.23 Bq per gram of carbon, which is where the counting challenge starts.