carbon 12

noun
  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
Dictionary.com 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.
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