Which statement accurately describes a half-life?

• A. It is the time required for all of the radioactive nuclei in a sample to decay.
• B. It is the time required for half of the radioactive nuclei in a sample to decay.
• C. It is the time required for the mass of a sample to double.
• D. It is the time required for a chemical reaction to reach equilibrium.

Answer: (B)

Verified step by step guidance

1. Understand that half-life is a concept used primarily in the context of radioactive decay and some chemical reactions involving first-order kinetics.
2. Recognize that half-life refers to the time it takes for a quantity (such as the number of radioactive nuclei) to reduce to half its initial amount, not the time for complete decay or doubling.
3. Recall the definition: The half-life (\(t_{1/2}\)) is the time required for half of the radioactive nuclei in a sample to decay, meaning only 50% of the original nuclei remain after one half-life.
4. Note that half-life is independent of the initial amount of substance and is a characteristic property of each radioactive isotope or first-order reaction.
5. Eliminate incorrect options by understanding that half-life is not about complete decay, mass doubling, or reaching chemical equilibrium, but specifically about the time for half the nuclei to decay.