These excited neutrons then collide with nitrogen atoms in the atmosphere, changing them into radioactive carbon-14 atoms.CARBON-14 IS ABSORBED (Figure 1b): Plants absorb this carbon-14 during photosynthesis.
These rapidly combine with oxygen atoms (the second most abundant element in the atmosphere, at 21%) to form carbon dioxide (CO).
This carbon dioxide, now radioactive with carbon-14, is otherwise chemically indistinguishable from the normal carbon dioxide in the atmosphere, which is slightly lighter because it contains normal carbon-12.
If we know what fraction of the carbon atoms are radioactive, we can also calculate how many radiocarbon atoms are in the lump.
Knowing the number of atoms that decayed in our sample over a month, we can calculate the radiocarbon decay rate.
It’s one of three naturally occurring carbon isotopes on the planet, and is found in just trace amounts (the vast majority of carbon found on Earth is carbon-12).