Other Radioisotopes Encountered in Everyday Life

A good example is carbon-14 which is a radioactive isotope of carbon. This radioisotope is made in the earth's upper atmosphereby a cosmogenic process. Cosmic rays bombard the earth's upper atmosphere and collide with atoms such as nitrogen. In this process the nitrogen loses a hydrogen atom and now becomes carbon-14, a radioactive isotope.

147N + 10n ----> 146C + 11H

This 14C is produced on a relatively continuous basis, and decays at a steady rate with a half-life of approximately 5700 years.

146C ----> 0-1e + 147N

Over the millennia these two reactions have reached an equilibrium concentration. Some of this carbon-14 reacts with oxygen and ends up as carbon dioxide (14CO2).

Carbon dioxide is a very stable molecule with a carbon covalently double-bonded to two oxygens in a linear geometry (O=C=O). Given that the half-life of carbon-14 is fairly long at 5730 years, 14CO2 is well mixed throughout the atmosphere.

Using your knowledge of biology, how would carbon-14 make its way into our bodies?

How about through the process of photosynthesis?

14CO2 + sun ----> (14H2O)n + O2

Now that we know that carbon-14 can be incorporated into sugars by the plant, it is easy to see how it can be incorporated into our own bodies through consumption.

Potassium-40 is a primordial radionuclide with a half-life of 1.28 x 109 years. Next time you are at the grocery store, look at some packages of light salts. A blend of potassium and sodium salts are used in these light salt mixtures which contain a small amount of potassium-40.

Thorium-232 is a primordial radionuclide with a half-life of 1.41 x 1010 years. Next time you go camping, you may just encounter thorium. As the sun is setting over the pacific ocean, you bring out your trusty white-gas lantern. Darkness comes on fast in these old-growth redwood forests, so the glow of a mantled lantern will be a welcomed site. Your match touches the mantle and the lantern shines to life. Say "hello" to thorium, for the chances are that your lantern's mantle contain thorium-232 to enhance luminescence.

Radon 222
This radionuclide is a colorless, odorless, inert gas which only has a half-life of 3.8 days. So where did it come from? If it was a primordial origin exclusively, it would have decayed away eons ago. The answer is that radon is a daughter product of uranium 238 which is a primordial radionuclide that still exists in measurable quantities and has a half-life on the order of billions of years.

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