The most abundant of the two stable isotopes of carbon, 126C, having six protons and six neutrons; it is the standard for atomic weight and is used to define the mole.(noun)
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Use "carbon-12" in a sentence
"Most of the carbon in the atmosphere’s carbon dioxide is carbon-12, which is not radioactive."
"Alpha particles from the decay cause a release of neutrons from the beryllium as it turns to carbon-12."
"The strongest evidence comes from measurements of the isotopic signature of carbon dioxide -- the amount of carbon-12, -13, and -14 in the atmosphere."