What is the importance of the isotope C14?

Radiocarbon dating is a widely used tool by archaeologists to find how old a sample of organic material is.

Carbon-14 is a radioactive isotope which accounts for about 1 in every trillion carbon atoms in the atmosphere. It is present in small amounts in most organic matter and has a half-life of approximately 5730 years.

Living organisms take in this carbon and use it for growth. Since carbon-14 is not chemically different from other carbon isotopes it has no detrimental effects on the organism and is used as if it was normal carbon.

If an organism dies the carbon remains in its body, and the C-14 decays through normal radioactive decay at a predictable rate. If the amount of carbon-14 in a sample is measured and compared with known levels of carbon-14 for the approximate time the sample was alive, the sample can be dated up to about 60,000 years old.

This is especially useful for dating trees or other plant-based samples as plants "fix" carbon-14 through photosynthesis and this carbon stays in the plant as it grows, and will remain in the sample for a long time after it dies.