What is carbon 14?

The word radioactivity suggests disastrous destruction, and many radioactive substances are indeed dangerous to handle. Radio carbon, however, is part of our daily lives. We breathe it with our air and eat it with our food, and radiocarbon, alias carbon 14, is radioactive.

Ordinary carbon is a common chemical element. Its slot on the periodic table of elements gives its atomic number as six. This means that its atom has six protons in its nucleus and six orbiting electrons. In 1961, scientists reshuffled their atomic weight system and the carbon atom was taken as a basis for all the other atoms. Its atomic weight is now 12, but in every sample of carbon material there are a few heavier atoms of carbon 14.

Nitrogen is next to carbon with an atomic number seven. If an atom of nitrogen loses a proton, it becomes an atom of carbon. We think this happens in the formation of carbon 14. Abundant supplies of nitrogen are present in the air, and the atmosphere is bombarded constantly by a barrage of speedy particles from cosmic rays. From time to time, one of these cosmic bullets strikes and shatters an atom of nitrogen.

In the crash, the nitrogen gains an extra neutron and loses one of its protons. With six protons, it must be an atom of carbon, but it is a top heavy, overweight atom of carbon 14. Unbalanced atoms of this kind tend to be unstable, and carbon 14, alias radiocarbon, is radioactive. In time, it shoots off its surplus particles and becomes ordinary carbon 12.

There is a certain percentage of carbon 14 in every sample of pure carbon and in all the half million known compounds of carbon. It is taken into plants and animals along with ordinary carbon. Radioactive breakdown always occurs at a fixed rate. For this reason, carbon 14 can be used to date fossils as old as 44,000 years.

When life ceases, carbon 14 is no longer added. The radioactive atoms in the fossil break down, and in exactly 5,600 years, half the original quota has become ordinary carbon. After another 5,600 years, Exactly half of the remaining carbon 14 will decay

Also. This ratio is the half life of radioactive carbon, and it is repeated every 5,600 years.

Radiocarbon was taken in by plants and animals that lived millions of years ago. Small traces were built into every cell and bone, every leaf and splinter. Scientists know how much carbon 14 to expect in a living plant or animal. An ion counter shows the amount that remains in a fossil. If half the original amount remains, the age of the fossil is 5,600 years. In another 5,600 years, the remaining radiocarbon will be reduced again by one half.