Which carbon isotope is used for dating organic materials?

Which carbon isotope is used for dating organic materials?

• A. Carbon-12
• B. Carbon-13
• C. Carbon-14
• D. Carbon-15

Answer: (C)

Radiocarbon dating uses carbon-14, a radioactive isotope, to determine age. In the atmosphere, carbon-14 is formed and becomes part of carbon dioxide, which plants fix and pass up the food chain to animals. Living organisms keep a constant ratio of carbon-14 to the stable carbon isotopes (carbon-12 and carbon-13). When an organism dies, it stops exchanging carbon, and carbon-14 begins to decay to nitrogen-14. With a half-life of about 5,730 years, the remaining carbon-14 decreases predictably over time. By measuring how much carbon-14 remains relative to carbon-12, we can estimate the time since death. The stable isotopes carbon-12 and carbon-13 don’t decay, so they don’t provide timing information, and carbon-15 isn’t used in this dating method. Therefore, carbon-14 is the isotope used for dating organic materials.

Radiocarbon dating uses carbon-14, a radioactive isotope, to determine age. In the atmosphere, carbon-14 is formed and becomes part of carbon dioxide, which plants fix and pass up the food chain to animals. Living organisms keep a constant ratio of carbon-14 to the stable carbon isotopes (carbon-12 and carbon-13). When an organism dies, it stops exchanging carbon, and carbon-14 begins to decay to nitrogen-14. With a half-life of about 5,730 years, the remaining carbon-14 decreases predictably over time. By measuring how much carbon-14 remains relative to carbon-12, we can estimate the time since death. The stable isotopes carbon-12 and carbon-13 don’t decay, so they don’t provide timing information, and carbon-15 isn’t used in this dating method. Therefore, carbon-14 is the isotope used for dating organic materials.