What is the half-life of a radioactive isotope?

The half-life of a radioactive isotope is defined as the period of time required for half of the radioactive atoms in a sample to decay into a different substance or to a more stable form. This concept is crucial in understanding radioactive decay and the behavior of isotopes over time. It essentially quantifies the rate at which a particular radioactive material loses its radioactive properties.

For instance, if you start with 100 grams of a radioactive substance with a half-life of one year, after one year, you would have 50 grams remaining; after another year, you would have 25 grams, and so forth. This decay continues in a predictable pattern, halving the amount of the substance with each passing half-life.

The other choices do not accurately reflect the concept of half-life. While the time it takes for an isotope to become stable or the duration of radiation exposure may relate to radioactive isotopes, they do not specifically define the half-life. Similarly, the total time an isotope remains hazardous is not synonymous with its half-life, as different isotopes may have varying levels of hazard even after they have gone through multiple half-lives.