In nuclear chemistry, what is a half-life?

The correct answer is the time required for half of the radioactive nuclei in a sample to decay. This concept of half-life is fundamental in nuclear chemistry, as it provides a measure of the rate at which a radioactive substance undergoes decay.

During each half-life period, half of the remaining radioactive nuclei in a sample will decay, meaning that after one half-life, 50% of the original quantity remains; after two half-lives, 25% remains; after three half-lives, 12.5% remains, and so on. This exponential decay process allows scientists to predict the remaining amount of a radioactive isotope after a given time, making it essential for applications like radiometric dating, medical treatments, and understanding nuclear reactions.

In contrast to the other options, the first choice misrepresents half-life, as it implies all radioactive nuclei decay, which can take vast amounts of time depending on the isotope. The third option refers to an individual nucleus, which does not align with the statistical nature of half-lives, as it describes the average behavior of many atoms in a large sample rather than the decay of a single nucleus. The last choice describes radioactivity becoming negligible, which is subjective and does not denote a specific time frame or statistical