What is the SI unit of radioactivity?

The SI unit of radioactivity is the Becquerel (Bq). This unit measures the rate of radioactive decay, specifically defined as one disintegration per second. It provides a standardized way to quantify radioactive activity, making it universally applicable in scientific and medical contexts.

The Curie (Ci) is an older unit that represents a significant quantity of radioactivity but is not part of the International System of Units (SI). The Gray (Gy) measures absorbed dose and describes the amount of radiation energy absorbed per unit mass of tissue, while the Radian (Rd) is a unit of angular measure, not associated with radioactivity. Thus, the Becquerel is the appropriate and internationally recognized SI unit for quantifying radioactivity.