What is defined as the time required for half of the atoms of a radioactive element to decay?

The term that describes the time required for half of the atoms of a radioactive element to decay is known as half-life. This concept is fundamental in the study of radioactivity and nuclear physics, as it provides a way to understand how quickly a radioactive substance will lose its radioactivity over time. Each radioactive isotope has a specific half-life that is not influenced by external conditions such as temperature, pressure, or chemical state.

Half-life is crucial for understanding the behavior of radioactive materials, including how long they remain hazardous to health and the environment. In radiological assessments, knowledge of half-life helps technicians predict how long it will take for a certain isotope to reduce to safer levels. This information is essential in fields such as radiology, nuclear medicine, and environmental science.

The other terms do not accurately capture this specific concept. Decay rate refers broadly to the speed at which a radioactive substance disintegrates but does not specify the time for half of its atoms to decay. Decay period may suggest a span of time but lacks the precision of "half-life." Existence duration implies a more generic timeframe without the specificity needed for radioactive decay processes. Thus, half-life is the precise term that accurately defines the concept in question.