What is the term for the time it takes for half of the unstable atoms to decay?

The term for the time it takes for half of the unstable atoms to decay is known as the half-life. This concept is essential in understanding radioactive decay processes. Half-life is a specific measure of the rate at which a radioactive isotope will decay; it indicates the time required for half of the original quantity of atoms in a sample to transform into a different state, often resulting in the release of energy or particles.

For example, if you have a sample of a radioactive substance, after one half-life, half of the original amount will have decayed, and after two half-lives, a quarter of the original amount will remain. This predictable nature of half-life is critical in applications ranging from radiometric dating in geology to medical treatments involving radioactive materials.

Other terms like decay period and decay constant refer to different aspects of radioactive decay but do not specifically denote the time for half the atoms to decay. A radioactive timeline, while it may imply a measure of time, lacks the specificity and established terminology that half-life provides in the context of radioactivity.