What term describes the time it takes for half the given mass of a radioactive element to change into a new element?

The correct term for the time it takes for half of a given mass of a radioactive element to decay into a different element is known as half-life. This concept is fundamental in the study of radioactivity and nuclear physics, as it quantifies the rate at which a radioactive substance transforms. Half-life provides a clear measure of the stability of a radioactive isotope, with shorter half-lives indicating that the material decays more quickly.

Understanding half-life is crucial because it allows scientists to predict how long it will take for a sample to reduce to a certain amount or to understand the behavior of radioactive materials in various contexts, such as in dating archaeological finds or managing radioactive waste.

The other terms mentioned do not accurately describe this specific time frame. The decay rate refers to how frequently decay events occur over time, while the decay constant is a proportionality factor that defines the rate of decay for a particular substance, but does not directly convey the time-related aspect of half-life. Exponential decay describes the process by which the quantity of a radioactive substance decreases over time, but again, it does not specifically measure the time it takes to reach half of the original quantity. Thus, half-life is the most accurate and relevant term for this concept.