Carbon-13 and carbon-14 are thus isotopes of carbon-12.Isotopes participate in the same chemical reactions but often at differing rates.
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Unfortunately the ratio of carbon-12 to carbon-14 has yet to reach a state of equilibrium in our atmosphere; there is more carbon-14 in the air today than there was thousands of years ago.
In order for carbon dating to be accurate, we must know what the ratio of carbon-12 to carbon-14 was in the environment in which our specimen lived during its lifetime.
The total mass of the isotope is indicated by the numerical superscript.
While the lighter isotopes C has decayed that what remains can no longer be measured. In 5,730 years half of the C in the atmosphere, and therefore in plants and animals, has not always been constant.