What unit measures the rate of radioactive decay?

The unit that measures the rate of radioactive decay is the Bequerel, which is defined as one disintegration per second. It provides a direct measure of how many atoms of a radioactive substance decay in a given period, thereby indicating the activity of the radioactive material.

The Curie is another unit used to measure radioactivity, specifically based on the activity of a quantity of radioactive material that disintegrates at a rate of 37 billion disintegrations per second. While it also represents a rate of decay, the Bequerel offers a more contemporary and standard approach as it is part of the International System of Units (SI).

Volt and Joule are units measuring electrical potential and energy respectively, and are not related to radioactivity or the rate of decay. These distinctions help clarify why Bequerel is the most appropriate choice for measuring radioactive decay.