Earth Science Regents Practice Exam 2025 - Free Regents Practice Questions and Study Guide

Half-life is a characteristic property of a radioactive isotope that indicates the time it takes for half of a sample to decay into a different element or isotope. This decay process is governed by the stability of the nucleus and the nature of the radioactive decay, which are intrinsic properties of the isotope itself.

The time elapsed since the formation of the radioactive isotope does not affect its half-life. The half-life remains constant regardless of how much time has passed or how much of the substance has already decayed. Each isotope has a specific half-life determined by its nuclear properties, which do not change over time. This means that regardless of when the isotope began decaying, its half-life is a fixed value.

In contrast, other factors such as temperature, pressure, and chemical state can influence the behavior and reactions involving the isotope but do not change the intrinsic half-life parameter. Understanding this distinction is crucial for using concepts of radioactive decay in nuclear science and Earth Science.