Which of the following best describes the half-life of a radioactive isotope?

• A. The time required for the isotope to double in mass.
• B. The time required for the isotope to reach chemical equilibrium.
• C. The time required for all atoms in a sample to decay.
• D. The time required for half of the atoms in a sample to decay.

Answer: (D)

Verified step by step guidance

1. Understand that the half-life of a radioactive isotope is a measure of time related to the decay process of the isotope's atoms.
2. Recall that radioactive decay is a random process where unstable nuclei lose energy by emitting radiation, transforming into different atoms or isotopes.
3. Recognize that the half-life is defined as the time required for half of the original number of radioactive atoms in a sample to decay, not the time for all atoms to decay or for the mass to double.
4. Note that the half-life is a constant for a given isotope and does not depend on the initial amount of the substance.
5. Therefore, the best description of half-life is: the time required for half of the atoms in a sample to decay.