Basic Principles of Carbon Dating Radiocarbon (carbon 14) is an isotope of the element carbon that is unstable and weakly radioactive. The stable isotopes are carbon 12 and carbon 13. Carbon 14 is continually being formed in the upper atmosphere by the effect of cosmic ray neutrons on nitrogen 14 atoms.

Why is carbon used in radioactive dating?

Carbon-14 is considered a radioactive isotope of carbon. Because its unstable, carbon-14 will eventually decay back to carbon-12 isotopes. And thats the key to radiocarbon dating. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive.