Radioactive Isotopes

About three-fourths of the elements have two or more stable isotopes and many have radioactive (unstable) ones, some of which can be useful, and others of which can be dangerous if we come into contact with them. A few of the more common radioactive isotopes and beneficial uses are noted in Table 2.

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Table 2 - Some Common Radioactive Isotopes
3H = Tritium = Luminous watch dials
14C = Carbon 14 = Radioactive dating
60Co = Cobalt 60 = Food irradiation
40K = Potassium 40 = Biological tracer
99Tc = Technetium 99 = Medical diagnosis
131I = Iodine 131 = Thyroid-function diagnosis and treatment
238Pu = Plutonium 238 = Spacecraft power supplies, pacemakers
241Am = Americium 241 = Smoke alarms
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All of the elements heavier than lead in the periodic table have multiple isotopes, and all are naturally radioactive; most of them decay into one of the stable lead isotopes. Uranium and thorium have the greatest number of isotopes - uranium with 22 isotopes and thorium with 28 - though most of these are not naturally occurring. As a rule of thumb, elements are happiest when they have about the same number of protons and neutrons. When there is a sizable difference, they tend to decay until there isn't.

So, what about this radioactive business? How does it work? How dangerous is it? And for how long?

A very interesting subject: Don't miss the next chapter.