How does radioactive half-life work?

Half-life is the time interval required for one-half of the atomic nuclei in a radioactive sample to undergo radioactive decay, or for the number of disintegrations per second to decrease by half.1

This process is statistical rather than immediate. Individual unstable nuclei decay at unpredictable times; however, in a large collection of identical nuclei, they decay over a period of time, similar to popcorn popping in a pan. As each nucleus decays, it emits particles and energy, often transforming into a different nuclear species or chemical element.21

Key characteristics of half-life include:
* Variability: Half-lives are specific to each radioactive isotope and can range from microseconds to billions of years.12
* Decay Chains: When a nucleus decays, the resulting "daughter" nucleus may also be radioactive, leading to a sequence of successive decays until a stable nucleus is produced.2
* Measurement: Scientists use the half-life to understand the stability of isotopes, such as uranium-238, which has a half-life of approximately 4.5 billion years.2