Science, Tech, Math › Science Understanding the Difference Between Carbon-12 and Carbon-14 Share Flipboard Email Print Gary Ombler / Getty Images Science Chemistry Periodic Table Basics Chemical Laws Molecules Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 24, 2020 Carbon-12 and carbon-14 are two isotopes of the element carbon. The difference between carbon-12 and carbon-14 is the number of neutrons in each of their atoms. This is how this works. The number given after the atom name indicates the number of protons plus neutrons in an atom or ion. Atoms of both isotopes of carbon contain 6 protons. Atoms of carbon-12 have 6 neutrons, while atoms of carbon-14 contain 8 neutrons. A neutral atom would have the same number of protons and electrons, so a neutral atom of carbon-12 or carbon-14 would have 6 electrons. Although neutrons do not carry an electrical charge, they have a mass comparable to that of protons, so different isotopes have different atomic weight. Carbon-12 is lighter than carbon-14. Carbon Isotopes and Radioactivity Because of the different number of neutrons, carbon-12 and carbon-14 differ in terms of radioactivity. Carbon-12 is a stable isotope; carbon-14, on the other hand, undergoes radioactive decay: 146C → 147N + 0-1e (half-life is 5720 years) Other Common Isotopes of Carbon The other common isotope of carbon is carbon-13. Carbon-13 has 6 protons, just like other carbon isotopes, but it has 7 neutrons. It is not radioactive. Although 15 isotopes of carbon are known, the natural form of the element consists of a mixture of only three of them: carbon-12, carbon-13, and carbon-14. Most of the atoms are carbon-12. Measuring the difference in the ratio between carbon-12 and carbon-14 is useful for dating the age of organic matter since a living organism is exchanging carbon and maintaining a certain ratio of isotopes. In a diseased organism, there is no exchange of carbon, but the carbon-14 that is present undergoes radioactive decay, so over time the change in isotope ratio becomes greater and greater.