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.
----> 146C +
This 14C is produced on a relatively
continuous basis, and decays at a steady rate with a half-life of
approximately 5700 years.
----> 0-1e +
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
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,
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?
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
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.
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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Return to the Cruising Chemistry