Half-lives of isotopes

Physical properties of this element have not been well investigated due to short half-lives of isotopes. The element is volatile may be chstdled in vacuum at room temperature in a glass apparatus and condensed in a dry ice trap. It is soluble in chloroform, ether, hexane and many other organic solvents. Solubility in water should be of low order. 

As the half lives of isotopes become shorter, they get more difficult to study. This is because short-lived isotopes are highly radioactive, which causes the emitted radiations to produce redox reactions, even in dilute solutions. Special apparatus is needed to study them, because of their intense radioactivity and the need to work rapidly. Further, due to limited quantities of the heavier elements, they can be studied only in very dilute solutions which sometimes behave strangely. 

Partial a half-lives decrease almost monotonically from 1012 s down to 10-9 s near Z = 126, see Figure 5c. The valley of (i-stable nuclei passes through Z = 114, N = 184. At a distance of about 20 neutrons away from the bottom of this valley, [) half-lives of isotopes have dropped down to values of one second [59],... 

Thus, the ratios of lead isotopes 204,206,207 and 208 can vary markedly depending on the source of the lead. One use of these ratios lies in determination of the ages of rocks from the abundances of the various isotopes and the half-lives of their precursor radioactive isotopes. 

The half-lives of the elements vary widely, as shown in Table 3.2. Some isotopes, nitrogen-14 for example, are stable and experience no natural radioactive decay. However, bombarding even a stable element with energetic alpha rays can cause transmutation. Rutherford discovered the proton when he created hydrogen from a stable isotope of nitrogen. 

The uranium and thorium decay-series contain radioactive isotopes of many elements (in particular, U, Th, Pa, Ra and Rn). The varied geochemical properties of these elements cause nuclides within the chain to be fractionated in different geological environments, while the varied half-lives of the nuclides allows investigation of processes occurring on time scales from days to 10 years. U-series measurements have therefore revolutionized the Earth Sciences by offering some of the only quantitative constraints on time scales applicable to the physical processes that take place on the Earth. 

If we consider this pair of radioactive isotopes for time scales greater than six half-lives of N2, Equation (3b) can be simplified. Because each decay series starts with a long-lived parent, it is commonly the case that A,2. In this case, after six half lives, e approaches zero and can be removed from the equation. For time scales such that 6T2 [Pg.6]

Decay of the nuclide itself. The conceptually simplest approach is to take a known quantity of the nuclide of interest, P, and repeatedly measure it over a sufficiently long period. The observed decrease in activity with time provides the half-life to an acceptable precision and it was this technique that was originally used to establish the concept of half-lives (Rutherford 1900). Most early attempts to assess half lives, such as that for " Th depicted on the front cover of this volume, followed this method (Rutherford and Soddy 1903). This approach may use measurement of either the activity of P, or the number of atoms of P, although the former is more commonly used. Care must be taken that the nuclide is sufficiently pure so that, for instance, no parent of P is admixed allowing continued production of P during the experiment. The technique is obviously limited to those nuclides with sufficiently short half-lives that decay can readily be measured in a realistic timeframe. In practice, the longest-lived isotopes which can be assessed in this way have half-lives of a few decades (e.g., °Pb Merritt et al. 1957). 

In these situations, addition of a tracer of unique isotopic composition is required, and the nature of the tracers added depends on the measurement technique. For example, short-lived and Th (with respective half-lives of 70 and 1.9 years) are commonly used as a tracer for alpha spectrometric analysis of U and Th, whereas longer-lived... 

Americium isotopes are transformed by radioactive decay. However, the half-lives of the principal americium isotopes, 241Am and 243Am, are very long, 432 and 7,370 years, respectively, and there is only a small amount of transformation over a human lifetime. 241Am is formed by the decay of 241Pu (half-life 14.4 years) and this can lead to a significant transformation of that isotope to 241 Am in humans, especially for 241Pu that is fixed in the bone. 

Unstable, silvery metal. The element was first discovered in the fallout from the first hydrogen bomb on the Bikini Atoll (1952), later produced by neutron bombardment of plutonium. Half-lives of the isotopes range from 20 to 401 days. "Relatively short-lived" in comparison to Einstein s formula E=m-c2, which is valid forever. Only of scientific interest. 

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