Bismuth-214, radioactive decay

Radon-222 [14859-67-7] Rn, is a naturally occuriing, iaert, radioactive gas formed from the decay of radium-226 [13982-63-3] Ra. Because Ra is a ubiquitous, water-soluble component of the earth s cmst, its daughter product, Rn, is found everywhere. A major health concern is radon s radioactive decay products. Radon has a half-life of 4 days, decayiag to polonium-218 [15422-74-9] Po, with the emission of an a particle. It is Po, an a-emitter having a half-life of 3 min, and polonium-214 [15735-67-8] Po, an a-emitter having a half-life of 1.6 x lO " s, that are of most concern. Polonium-218 decays to lead-214 [15067-28A] a p-emitter haviag = 27 min, which decays to bismuth-214 [14733-03-0], a p-emitter haviag... 

The name comes from the Greek aktis, meaning beam or ray. It was discovered by Andre-Louis Debierne (1874-1949) in 1899 and independently by Fritz Giesel (1852-1927) in 1902. It exists in very small quantities in association with uranium ores. Actinium has few uses outside the laboratory, but its discovery was important for the development of chemistry and physics, as it was one of the materials used to study radioactive decay, since it breaks down into thorium, radium, radon, bismuth, polonium, and isotopes of lead. 

A lot of important information about the chemical elements is contained in a periodic table. The periodic table is a tabular illustration of the elements. Each element is listed with its chemical symbol and atomic number. The layout of the periodic table demonstrates a series of related, or periodic, chemical properties. Elements are arranged by increasing atomic number (the number of protons). Elements with similar properties fall into the same vertical columns. Elements with atomic numbers 83 or higher (above bismuth) are unstable and undergo radioactive decay over time. There aie many examples of this table and some of the interactive versions on the Internet provide many details about the full name of the element, isotopes, atomic mass, and other information. 

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. 

Polonium occurs in U and Th minerals as a product of radioactive decay series. It was first isolated from pitchblende which contains less than 0.1 mg of Po per ton. The most accessible isotope is 210Po (a, 138.4d) obtained in gram quantities by irradiation of bismuth in nuclear reactors ... 

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. 

C. It occurs naturally by radioactive decay from uranium and thorium isotopes. Astatine forms at least 20 isotopes, the most stable astatine-210hasahalf-lifeof8.3 hours. It can also be produced by alpha bombardment of bismuth-200. Astatine is stated to be more metallic than iodine at least 5 oxidation states ate known in aqueous solutions. It will form interhalogen compounds, such as Atl and AtCl. The existence of At2 has not yet been established. The element was synthesized by nuclear bombardment in 1940 by D. R. Corson, K. R. Mac-Kenzie, and E. Segre at the University of California. 

Bismuth, atomic number 83, contains the heaviest stable nucleus. All elements heavier than bismuth have unstable nuclei and decay radio actively, some faster, some slower. In addition, some isotopes of elements with atomic number lower than 83 are also unstable and undergo radioactive decay. Beginning with U-238, the heaviest naturally occurring element, we can construct a radioactive decay... 

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. 

Write nuclear equations to represent (a) a-particle emission by Rn and (b) radioactive decay of bismuth-215 to polonium-215. 

ISOTOPES All 41 isotopes of astatine are radioactive, with half-lives ranging from 125 nanoseconds to 8.1 hours. The isotope As-210, the most stable isotope with an 8.1-hour half-life, is used to determine the atomic weight of astatine. As-210 decays by alpha decay into bismuth-206 or by electron capture into polonium-210. 

All isotopes of all elements beyond bismuth (Z 83) are radioactive. In particular, isotope 227 of actinium (Z = 89) decays mainly with the emission of particles, forming a0Th227 (Chap. 27). It has been shown, however, that about 1 percent of this actinium isotope decays in a differ-... 

What can be done to combat radon pollution indoors The first step is to measure the radon level in the basement with a rehable test kit. Short-term and long-term kits are available (Figure 17.28). The short-term tests use activated charcoal to collect the decay products of radon over a period of several days. The container is sent to a laboratory where a technician measures the radioactivity (y rays) from radon-decay products lead-214 and bismuth-214. Knowing the length of exposure, the lab technician back-calculates to determine radon concentration. The long-term test kits use a piece of special polymer film on which an a particle will leave a track. After several months exposure, the film is etched with a sodium hydroxide solution and the num-... 

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. 

Actinium — (Gr. aktis, aktinos, beam or ray), Ac at. wt. (227) at. no. 89 m.p. 1050°C, b.p. 3198°C sp. gr. 10.07 (calc.). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Thirty-four isotopes and isomers are now recognized. All are radioactive. Actinium-227, a decay product of uranium-235, is an alpha and beta emitter with a 21.77-year half-life. Its principal decay products are thorium-227 (18.72-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300°C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.77-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. Actinium-225, with a purity of 99%, is available from the Oak Ridge National... 

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