carbon 12

American  

Also 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.

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carbon 12 Scientific  

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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Etymology

Origin of carbon 12

First recorded in 1940–45

Compare meaning

How does carbon-12 compare to similar and commonly confused words? Explore the most common comparisons:

• carbon 12 vs. carbon 14

Example Sentences

But if Perseverance’s sample is found to contain not only methane but methane rich in an isotope called carbon 12, that could change.

From Scientific American • Nov. 10, 2021

They ruled out earlier and later Miyake events based on the carbon 14 to carbon 12 ratios measured in the wood, which vary in known ways over centuries.

From Seattle Times • Oct. 21, 2021

Carbon 13 usually comes from inorganic sources, such as volcanoes, while carbon 12 is tied to living things.

From Washington Times • Jun. 11, 2017

The element carbon usually has six protons and six neutrons, and when it does it is called carbon 12.

From Forbes • May 21, 2010

The amount of carbon 12 stays the same, but the unstable carbon 14 begins to disintegrate.

From Time Magazine Archive