Explain the method of radio-carbon dating to determine the age of plant and animal fossils.

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ncchemist | eNotes Employee

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Carbon in nature is found in different isotopes, meaning that the number of neutrons in the nucleus can differ.  The most common carbon isotope found in nature is called C-12, meaning that the nucleus contains 6 protons and 6 neutrons.  But <1% of all naturally occuring carbon is the C-14 isotope, meaning that the nucleus has 6 protons and 8 neutrons.  The C-13 isotope is naturally mildly radioactive and beta decays at a constant rate (called the half life).  Once an organism dies it no longer accumulates any additional C-14 in its body and the radioactive decay begins to occur at a steady rate.  So the amount of C-14 can be measured and then based on the decay rate you can count back in time to when the organism died.  Keep in mind that there is a margin of error here so radiocarbon dating will give you date range and not really an exact year.

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