Uses of Isotopes

Radioactive and stable isotopes alike have many applications in science and medicine. We have previously described the use of isotopes in the study of reaction mechanisms [Ml Section 14.5] and in dating artifacts (page 806). In this section we will discuss a few more examples. 

The formula of the thiosulfate ion is SoOi . For some years, chemists were uncertain as to whether the two sulfur atoms occupied equivalent positions in the ion. The thiosulfate ion is prepared by treating the sulfite ion with elemental sulfur  

When thiosulfate is treated with dilute acid, the reaction is reversed. The sulfite ion is re-formed, and elemental sulfur precipitates  

If this sequence is started with elemental sulfur enriched with the radioactive sulfur-35 isotope, the isotope acts as a label for S atoms. All the labels are found in the sulfur precipitate none of them appears in the final sulfite ions. As a result, the two atoms of sulfur in S2O3 are not structurally equivalent, as would be the case if the structure were 

If the. sulfur atoms were equivalent, the radioactive isotope would be present in both the elemental sulfur precipitate and the sulfite ion. Based on spectroscopic studies, we now know that the structure of the thiosulfate ion is 

There is no critical mass in a fusion bomb, and the force of the explosion is limited only by the quantity of reactants present. Thermonuclear bombs are described as being cleaner than atomic bombs because the only radioactive isotopes they produce are tritium, which is a weak j8-particle emitter (ii/ = 12.5 years), and the products of the fission starter. Their damaging effects on the environment can be aggravated, however, by incorporating in the construction some nonfission-able material such as cobalt. Upon bombardment by neutrons, cobalt-59 is converted to cobalt-60, which is a very strong y-ray emitter with a half-life of 5.2 years. The presence of radioactive cobalt isotopes in the debris or fallout from a thermonuclear explosion would be fatal to those who sm-vived the initial blast. 

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See also in sourсe #XX -- [ , ]

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