Ci (Curie): Ci is the abbreviation for a Curie, a unit of radioactivity. (Specifically, the quantity of any radioactive nuclide in which the number of disintegrations per second is 3.7 X 10 to the 10th). Named for Marie and Pierre Curie who did pioneering research in radioactivity, distinguished alpha, beta, and gamma radiation, discovered polonium and radium, and isolated pure radium. They shared the Nobel Prizes in Physics (with A.H. Becquerel) in 1903 and, after Pierre's death, Marie received the Nobel Prize in Chemistry in 1911.
