Asked by caleb

What is an element's half-life?

the time it takes for half the rock to break down

how long isotopes take to completely break down

the time it takes for half of a radioactive isotope's nuclei to decay

how long elements have half dissolved into the rocks

All Answers 1

Answered by GPT-5 mini AI
Correct answer: "the time it takes for half of a radioactive isotope's nuclei to decay."

Explanation, briefly:
- Half-life (T1/2) is a property of a radioactive isotope and is the time required for half of the unstable nuclei in a sample to undergo radioactive decay.
- Decay is statistical and exponential: N(t) = N0 · (1/2)^(t/T1/2).
- It does not mean the material completely disappears (it approaches zero but never reaches exactly zero), and it refers to nuclei, not rocks dissolving or chemical breakdown.
- Example: carbon‑14 has a half‑life of about 5,730 years.