Radioactive Elements and Compounds

Radioactive materials are a part of everyday life. Uranium, U, is a radioactive metallic element. Uranium has three naturally occurring isotopes uranium 234 

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Raschella, D. L. "Solution Microcalorimeter for Measuring Heats of Solution of Radioactive Elements and Compounds" Ph.D. Dissertation, The University of Tennessee, Knoxville, December 1978 U.S. Department of Energy Document No. 0R0-4447-081, 1978. 

All the analytical techniques used in conventional chemistry may be used for the separation and isolation of radioactive elements and compounds in macro or trace concentrations. The precipitation method was amply demonstrated by the early radiochemists M. Curie, Debieme, Rutherford, Hahn, etc., for the separation, concentration and identification of the naturally occurring radioactive elements. However, in 9.2.1-9.2.4 we have pointed out the many pitfalls in working with tracer concentrations in solutions containing precipitates, etc, as well as in the use of electrochemical methods ( 9.2.5). 

Intensity of Radiation Radiation Exposure Radioactive Elements and Compounds Uranium Compounds Radium Compounds... 

For many of the analytical techniques discussed below, it is necessary to have a source of X-rays. There are three ways in which X-rays can be produced in an X-ray tube, by using a radioactive source, or by the use of synchrotron radiation (see Section 12.6). Radioactive sources consist of a radioactive element or compound which spontaneously produces X-rays of fixed energy, depending on the decay process characteristic of the radioactive material (see Section 10.3). Nuclear processes such as electron capture can result in X-ray (or y ray) emission. Thus many radioactive isotopes produce electromagnetic radiation in the X-ray region of the spectrum, for example 3He, 241Am, and 57Co. These sources tend to produce pure X-ray spectra (without the continuous radiation), but are of low intensity. They can be used as a source in portable X-ray devices, but can be hazardous to handle because they cannot be switched off. In contrast, synchrotron radiation provides an... 

Now that we have an understanding of radioactive isotopes and their utility in constraining the timing and rates of nebular, planetesimal, and planetary processes, we will turn our attention to the most volatile elements and compounds. Stable isotopes in them provide additional constraints on cosmochemical processes. 

The distribution of a radioactive element or compound in a composite matrix can made visible either to the naked eye or under a microscope by means of autoradiography. The technique is based on the blackening of photographic films when exposed to nuclear radiation (cf. 7.2 and 7.10). The technique is best illustrated by an example. 

Ten years after the invention of the cyclotron, the nuclear reactor was invented. In Germany in December, 1938, Hahn and Strassman discovered fission a uranium atom could be split into smaller elements. In December 1942, Enrico Fermi and his colleagues built the first nuclear reactor in Chicago as part of the Manhattan Project. The nudear reactor was able to provide a far wider source of radioactive dements and compounds at much lower cost than the cydotron. 

Radiochemical methods of analysis are used in a wide range of analytical applications. Not only can these methods be used to obtain information regarding the nature and quantities of substances present in materials of interest, but radioactive elements can also be employed as tracers to study various physicochemical processes. Radioactive substances can be used to follow the movement of elements or of specific compounds in soils and plants, the absorption of elements in the body, and the selfdiffusion of lead atoms in metallic lead, among other applications. Although these tracer applications are of great practical value, the present chapter will be concerned only with applying radioactivity to determining the presence and quantity of elements and compounds in various materials—that is, the use of radioactivity in chemical analysis. 

Classical liquid radiochromatography has been used mainly for preparative work, and analytical applications have been rare. The method has been important in the separation and isolation of new radioactive elements and labeled compounds. Technical progress has made this method applicable to the direct analytical determination of biochemically important compounds, labeled preparations, components of food and environmental samples. 

Labeled compounds offer many advantages for food science. The extreme sensitivity of radioactivity measurement enables one to determine and characterize biologically important trace elements and compounds (e.g., pesticides and pesticide residues) in food samples. 

Relatively little is known about the chemistry of the radioactive Group I element francium. Ignoring its radioactivity, what might be predicted about the element and its compounds from its position in the periodic table ... 

Since the discovery of the first noble gas compound, Xe PtF (Bartlett, 1962), a number of compounds of krypton, xenon, and radon have been prepared. Xenon has been shown to have a very rich chemistry, encompassing simple fluorides, XeF2> XeF, and XeF oxides, XeO and XeO oxyf luorides, XeOF2> XeOF, and Xe02 2 perxenates perchlorates fluorosulfates and many adducts with Lewis acids and bases (Bartlett and Sladky, 1973). Krypton compounds are less stable than xenon compounds, hence only about a dozen have been prepared KrF and derivatives of KrF2> such as KrF+SbF, KrF+VF, and KrF+Ta2F11. The chemistry of radon has been studied by radioactive tracer methods, since there are no stable isotopes of this element, and it has been deduced that radon also forms a difluoride and several complex salts. In this paper, some of the methods of preparation and properties of radon compounds are described. For further information concerning the chemistry, the reader is referred to a recent review (Stein, 1983). 

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