Curie (Ci)

Radioactive decay

2.22×10¹² dpm

The curie (symbol Ci) is a unit of radioactivity, defined as 1 Ci = 3.7×10¹⁰ decays per second. This is roughly the activity of 1 gram of the radium isotope ²²⁶Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie (for whom the unit is named).