Bismuth nuclides

Fe. What nuclide could be formed by bombarding the stable bismuth nuclide with this nuclide ... 

It will be recalled that is 100% abundant and is the heaviest stable nuclide of any element (p. 550), but it is essential to use very high purity Bi to prevent unwanted nuclear side-reactions which would contaminate the product Po in particular Sc, Ag, As, Sb and Te must be <0.1 ppm and Fe <10ppm. Polonium can be obtained directly in milligram amounts by fractional vacuum distillation from the metallic bismuth. Alternatively, it can be deposited spontaneously by electrochemical replacement onto the surface of a less electropositive metal... 

The origin of chemical elements has been explained by various nuclear synthesis routes, such as hydrogen or helium burning, and a-, e-, s-, r-, p- and x-processes. "Tc is believed to be synthesized by the s (slow)-process in stars. This process involves successive neutron capture and / decay at relatively low neutron densities neutron capture rates in this process are slow as compared to /1-decay rates. The nuclides near the -stability line are formed from the iron group to bismuth. 

Radon daughters are deposited on the surface of mucus lining the bronchi. It is generally assumed that the daughter nuclides, i.e. polonium-218 (RaA), lead-214 (RaB) and bismuth-214 (RaC), remain in the mucus and are transported towards the head. However, one dosimetric model assumes that unattached radon daughters are rapidly absorbed into the blood (Jacobi and Eisfeld, 1980). This has the effect of reducing dose by about a factor of two. Experiments in which lead-212 was instilled as free ions onto nasal epithelium in rats have shown that only a minor fraction is absorbed rapidly into the blood (Greenhalgh et al., 1982). Most of the lead remained in the mucus but about 30% was not cleared in mucus and probably transferred to the epithelium. 

Astatine - the atomic number is 85 and the chemical symbol is At. The name derives from the Greek astatos for unstable since it is an unstable element. It was first thought to have been discovered in nature in 1931 and was named alabamine. When it was determined that there are no stable nuclides of this element in nature, that claim was discarded. It was later shown that astatine had been synthesized by the physicists Dale R. Corson, K. R. Mackenzie and Emilio Segre at the University of California lab in Berkeley, California in 1940 who bombarded bismuth with alpha particles, in the reaction Bi ( He, 2n ) "At. Independently, a claim about finding some x-ray lines of astatine was the basis for claiming discovery of an element helvetium, which was made in Bern, Switzerland. However, the very short half-life precluded any chemical separation and identification. The longest half-life associated with this unstable element is 8.1 hour °At. 

Numerous nuclear reactions have been employed to produce astatine. Three of these are particularly suited for routine preparation of the relatively long-lived isotopes with mass numbers 209, 210, and 211. The most frequently used is the ° Bi(a,xn) At (a = 1-4) reaction, in which bismuth 44, 74,120) or bismuth oxide (7,125) is bombarded by 21-to 40-MeV a-particles. The ° Bi(He, xn) At reaction can also be used to produce isotopes of astatine 152), the nuclear excitation functions (62) favor a predominant yield of ° At and °At. The routine preparation of astatine is most conveniently carried out through the ° Bi(a,xn) At nuclear reactions, from which a limited spectrum of astatine nuclides may be derived. The excitation functions for these nuclear reactions have been studied extensively (78, 89, 120). The... 

In this section, we present results dealing with the discovery of elements 107 to 112 using cold fusion reactions based on lead and bismuth targets. A detailed presentation and discussion of the decay properties of elements 107 to 109 and of elements 110 to 112 was given in previous reviews [15,20,21], Presently known nuclei are shown in the partial chart of nuclides in Figure 2. 

All elements beyond bismuth in the Periodic Table are radioactive, most of these having several isotopes (or nuclides), each with a characteristic half-life. A small number of elements of low atomic number (K, Rb, Sm, Lu, Re, and perhaps La and H) each have one naturally occurring radioisotope also. In addition, over 700 radioisotopes have been made artificially (p. 466). 

Figure 8.21. Mass dispersion for nuclear reactions of protons with heavy nuclides. Examples reaction of protons of various energies with bismuth (according to J. M. Miller, J. Hudis, Annu. Rev. Nucl. Sci. 9 159 (1959)).

Stable nuclides are found in a narrow band, the band of stability, that ends at Z= 83 (bismuth). 

Consider three isotopes of bismuth ssBi, 80i> and gsBi. Bismuth-209 is stable. One of the other nuclides undergoes beta emission, and the remaining nuclide undergoes electron capture. Identify the isotope that makes each of these changes, and explain your choices. 

Bismuth-211 atoms undergo an alpha emission and beta emission before they reach a stable nuclide. What is the final product ... 

In December 1994, the nuclide roentgenium-272, niRg, was made from the bombardment of bismuth-209 atoms with nickel-64 atoms. Write a nuclear equation for this reaction. (One or more neutrons may be released in this type of nuclear reaction.)... 

As can be seen in Figure 1, radon itself and its polonium daughter products are alpha emitting nuclides, while the isotopes of lead and bismuth produced are beta/ gamma emitters. The short half-lives of the daughter products prior to Pb (Table 2) result in the rapid production of a mixture of airborne radioactive materials which may attain equilibrium concentrations within a relatively short time. The half-life of °Pb is 22 years and at this point in the decay chain any activity inhaled is largely removed from airways in which it is deposited before any appreciable decay occurs. 

Alpha radioactivity is found principally among elements beyond bismuth in the periodic table. AH the nuclides important as fissionable or fertile material are alpha emitters, with half-lives and decay energies given in Table 2.1. These half-lives are so long that depletion of these fuel species by radioactive decay is not important, but all these nuclides are toxic, especially plutonium, which is even more toxic than radium. 

All nuclides with Z > 83 are unstable. Bismuth-209 is the heaviest stable nuclide. Therefore, the largest members of Groups 1A(1), 2A(2), 4A(14), 6A(16), 7A(17), and 8A(18) are radioactive, as are all the actinides (the 5/inner-transition elements) and the elements of the fourth rf-block transition series (Period 7). 

If a graph is made (Fig. 3.1) of the relation of the number of neutrons to the number of protons in the known stable nuclei, we find that in the light elements stability is achieved when the number of neutrons and protons are approximately equal (N = Z). However, with increasing atomic number of the element (i.e. along the Z-line), the ratio of neutrons to protons, the NIZ ratio, for nuclear stability increases from unity to iqiproximately l.S at bismuth. Thus pairing of the nucleons is not a sufficient criterion for stability a certain ratio NIZ must also exist. However, even this does not suffice for stability, because at high Z-values, a new mode of radioactive decay, a-emission, appears. Above bismuth the nuclides are all unstable to radioactive decay by a-particle emission, while some are unstable also to / -decay. 

Nuclides are said to be either stable (nonradioactive) or unstable (radioactive). Elements that have atomic numbers greater than 83 (bismuth) are naturally radioactive, although some of the nuclides have extremely long half-lives. Some of the naturally occurring nuclides of elements 81, 82, and 83 are radioactive, and some are stable. Only a few naturally occurring elements that have atomic numbers less than 81 are radioactive. However, no stable isotopes of element 43 (technetium) or of element 61 (promethium) are known. 

Radioactivity is believed to be a result of an unstable ratio of neutrons to protons in the nucleus. Stable nuclides of elements up to about atomic number 20 generally have about a 1 1 neutron-to-proton ratio. In elements above number 20, the neu-tron-to-proton ratio in the stable nuclides gradually increases to about 1.5 1 in element number 83 (bismuth). When the neutron-to-proton ratio is too high or too low, alpha, beta, or other particles are emitted to achieve a more stable nucleus. 

Bismuth-211 deca) by alpha emission to give a nuclide that in turn decays by beta emission to yield a stable nuclide. Show these two steps with nuclear equations. 

Windscale The Windscale (now called Shellafield) Reactor No. 1 was partially consumed by combustion in October 1957, resulting in the release of fission products to the surrounding countryside. The reactor was an air-cooled graphite-moderated natural-uranium reactor employed primarily for plutonium production. The radionuclides (740 TBq), Cs (22 TBq), Ru (3 TBq), and Xe (1.2 PBq) were released. In addition to those fission products, 8.8 TBq of Po was also released, because the nuclide was produced by neutron irradiation of bismuth. The released radionuclides moved from Windscale to the south, southeast, and to London, and they contaminated vast grasslands. The collective dose is estimated to be 2,000 man-Sv in the contaminated area. 

The Karlsruhe Chart of the Nuclides has this same basic structure but with the addition of all known radioactive nuclides. The heaviest stable element is bismuth (Z = S3, N = 126). The figure also shows the location of some high Z unstable nuclides - the major thorium (Z = 90) and uranium (Z = 92) nuclides. Theory has predicted that there could be stable nuclides, as yet unknown, called superheavy nuclides on an island of stability at about Z = 114, A = 184, well above the current known range. 

Theoretical physicists predicted the existence of the island of stability, centered at element 114 with mass number 298, in the 1960s. The term stability refers here to that of the atomic nucleus. An unstable nucleus tends to fall apart by radioactive decay—a piece spontaneously flies off the nucleus, leaving a different one behind. Approximately 275 nuclides are completely stable, or nonradioactive. All of these nuclides have atomic numbers (or numbers of protons) no greater than 83 (the atomic number for the element bismuth). Beyond bismuth, all elements are radioactive and become increasingly unstable. In fact, none of the original, primeval elements past uranium (element 92)—the transuranium elements—exists any longer they have long since vanished by radioactive decay. Scientists have made transuranium elements in the laboratory, however. 

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