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Dig into Montana Before History: 11K Years of Hunter-Gatherers in the Rockies and Plains by D. H. MacDonald, Ph.D. See our online store book collection.
The atomic nucleus shown in the top half of this picture is carbon-14. The 14C nucleus has 6 protons plus 8 neutrons, giving it an atomic mass of 14.
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Original artwork by Windows to the Universe staff (Randy Russell).


Carbon-14 is an isotope of the element carbon. All carbon atoms have 6 protons in their nucleus. Most carbon atoms also have 6 neutrons, giving them an atomic mass of 12 ( = 6 protons + 6 neutrons). Carbon-14 atoms have two extra neutrons, giving them a total of 8 neutrons. Carbon-14 has an atomic mass of 14 ( = 6 protons + 8 neutrons). The extra neutrons make the nucleus of carbon-14 unstable. Carbon-14 is radioactive!

Radioactive carbon-14 (also written as 14C) has a half-life of 5,730 years. 14C is used to determine the ages of artifacts that were once living (such as pieces of wood, teeth or bones, coral skeletons, etc.) via a technique called "carbon-14 dating" or "radiocarbon dating".

Some of the carbon dioxide gas in Earth's atmosphere contains 14C atoms. The supply of CO2 molecules which contain carbon-14 is continuously replenished in our atmosphere. Cosmic rays from space sporadically strike nitrogen atoms, converting some common nitrogen-14 atoms into radioactive carbon-14 atoms.

Last modified June 4, 2010 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA