What is the term for the length of time required for half of the radioactive atoms in a sample to decay?

The term for the length of time required for half of the radioactive atoms in a sample to decay is known as half-life. This concept is fundamental in understanding radioactive decay and the stability of isotopes. During one half-life, the amount of the original radioactive substance decreases by half, which provides a consistent measure for scientists to predict how long it will take for a given sample to lose a significant portion of its radioactivity. This characteristic helps in various fields, including archaeology (for carbon dating), medicine (radiotherapy), and nuclear energy (understanding the safety and longevity of radioactive materials).

Other terms presented in the choices relate to different aspects of nuclear physics. For instance, activity refers to the number of decays per unit time, while the decay constant represents the probability of decay of a single atom. Nuclear fission is a process in which the nucleus of an atom splits into smaller parts, often producing a chain reaction and is not directly related to the concept of half-life.