Carbon dating level chemistry
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.
Many people assume that rocks are dated at “millions of years” based on radiocarbon (carbon-14) dating. The most well-known of all the radiometric dating methods is radiocarbon dating.
Carbon-14 can yield dates of only “thousands of years” before it all breaks down.
The reason is that, as long as the organism is alive, it replaces any carbon molecule that has decayed into nitrogen.
After plants and animals perish, however, they no longer replace molecules damaged by radiocarbon decay.
CARBON-14 IS ABSORBED (Figure 1b): Plants absorb this carbon-14 during photosynthesis.Radiocarbon then enters animals as they consume the plants (Figure 1b).So even we humans are radioactive because of trace amounts of radiocarbon in our bodies.We can measure in the laboratory how many carbon-14 atoms are still in the skull.If we assume that the mammoth originally had the same number of carbon- 14 atoms in its bones as living animals do today (estimated at one carbon-14 atom for every trillion carbon-12 atoms), then, because we also know the radiocarbon decay rate, we can calculate how long ago the mammoth died. This dating method is similar to the principle behind an hourglass.6 The sand grains that originally filled the top bowl represent the carbon-14 atoms in the living mammoth just before it died.