单词	carbon 12
释义	carbon 12 noun : an isotope of carbon of mass number 12 that is the most abundant carbon isotope and is used as a standard for measurements of atomic weight Example Sentences Recent Examples on the Web Carbon has two stable isotopes, measured as either carbon 12 or carbon 13. Ashley Strickland, CNN, 17 Jan. 2022 But if Perseverance’s sample is found to contain not only methane but methane rich in an isotope called carbon 12, that could change. Jonathan O'callaghan, Scientific American, 10 Nov. 2021 So researchers compare the amount of carbon 14 with the levels of carbon 12 and carbon 13 to determine how much time has passed since an organism perished. Scott Hershberger, Scientific American, 4 Aug. 2020 Chemically, carbon 14 behaves exactly like its stable siblings (carbon 12 and carbon 13), allowing plants to absorb it during photosynthesis and then pass it up the food chain. Scott Hershberger, Scientific American, 4 Aug. 2020 By controlling the magnetic field and other conditions inside the cannon, the researchers cause the carbon 14 atoms to veer away from the carbon 12 atoms and other elements. Carl Zimmer, The Atlantic, 20 Mar. 2020 The key is in the rock’s atomic composition; organisms that use sunlight for energy incorporate a lighter version of carbon, called carbon 12, over the heavier carbon 13. Peter Byrne, Quanta Magazine, 24 Apr. 2014 See More Word History First Known Use 1936, in the meaning defined above
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