carbon 12

  1. the isotopic carbon atom that comprises 99 percent of naturally occurring carbon, and that since 1961 has been used as the standard for atomic weight by representing a unit of 12.00000.
Also car·bon-12 [kahr-buh n-twelv] /ˈkɑr bənˈtwɛlv/.

Origin of carbon 12

First recorded in 1940–45 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

carbon 12 in Science

carbon 12

  1. A stable isotope of carbon, having six protons and six neutrons in the nucleus. Carbon 12 makes up most naturally occurring carbon.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.