Becquerel ($\mathrm{Bq}={\mathrm{s}}^{-1}$)

Becquerel (symbol: Bq) is the SI unit of radioactivity. It measures the activity of a quantity of radioactive material, specifically the number of disintegrations (or decay events) that occur in a sample per second. One becquerel is defined as one disintegration per second. The unit is named after Henri Becquerel, a French physicist who discovered radioactivity in 1896.