We can estimate the amount of carbon-14 that has decayed by measuring the amount of carbon-14 to carbon-12. With this information, we can tell how long ago the organism died. It decays quickly compared to some other unstable isotopes.

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All atoms of a given element contain the same number of protons. Atoms of an element with different numbers of neutrons are called isotopes. The half-life is the time it takes for half of a given amount of an isotope to decay.

Only a tiny percentage of carbon atoms are carbon-14. Figure below shows carbon dioxide, which forms in the atmosphere from carbon-14 and oxygen.

The rate of decay of unstable isotopes can be used to estimate the absolute ages of fossils and rocks. The best-known method of radiometric dating is carbon-14 dating. A living thing takes in carbon-14 (along with stable carbon-12). Compare and contrast carbon-14 dating and potassium-40 dating.

As the carbon-14 decays, it is replaced with more carbon-14. Scientists estimate the ages of rock layers in order to better understand Earth’s history and the history of life.

These isotopes have much longer half-lives than carbon-14.

Because they decay more slowly, they can be used to date much older specimens.

After the organism dies, it stops taking in carbon. The carbon-14 that is in its body continues to decay. Apply lesson concepts to infer how many protons and neutrons are found in each atom of carbon-13. How useful would carbon-13 be for radiometric dating?

So the organism contains less and less carbon-14 as time goes on.

Radiocarbon dating was invented in the 1940s by Willard F. Radioactive dating is used in research fields, such as anthropology, palaeontology, geology and archeology.