Carbon dating worksheet
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.As a result it is always undergoing natural radioactive decay while the abundances of the other isotopes are unchanged.Carbon-14 is most abundant in atmospheric carbon dioxide because it is constantly being produced by collisions between nitrogen atoms and cosmic rays at the upper limits of the atmosphere.Radioactive and non-radioactive carbon dioxide mix throughout the atmosphere, and dissolve into the oceans.Through photosynthesis carbon dioxide enters plants and algae, bringing radiocarbon into the food chain.These excited neutrons then collide with nitrogen atoms in the atmosphere, changing them into radioactive carbon-14 atoms.
Carbon-13 and carbon-14 are thus isotopes of carbon-12.
The rate at which C atoms, half of them will decay in 5730 years.
Since this rate is slow relative to the movement of carbon through food chains (from plants to animals to bacteria) all carbon in biomass at earth's surface contains atmospheric levels of C is present at atmospheric levels, the molecule must derive from a recent plant product.
By comparing the surviving amount of carbon-14 to the original amount, scientists can calculate how long ago the animal died.
Since the atmosphere is composed of about 78% nitrogen,2 a lot of radiocarbon atoms are produced—in total about 16.5 pounds (7.5 kg) per year.