Which of the following is an example of a radioactive isotope?

• A. carbon-14
• B. neon-22
• C. neon-20
• D. carbon-12

Answer: (A)

Verified step by step guidance

1. Understand what a radioactive isotope is: it is an isotope of an element that has an unstable nucleus and undergoes radioactive decay, emitting radiation to become more stable.
2. Identify the isotopes listed: carbon-14, neon-22, neon-20, and carbon-12. Each isotope differs by the number of neutrons in the nucleus.
3. Recall that carbon-12 and neon isotopes (neon-20 and neon-22) are stable isotopes, meaning they do not undergo radioactive decay.
4. Recognize that carbon-14 is a well-known radioactive isotope of carbon, used in radiocarbon dating because it decays over time.
5. Conclude that among the options, carbon-14 is the radioactive isotope because it has an unstable nucleus and undergoes radioactive decay.