Radium/radon isotopes

Uranium-238 emits an alpha particle to become an isotope of thorium. This unstable element emits a beta particle to become the element now known as Protactinium (Pa), which then emits another beta particle to become an isotope of uranium. This chain proceeds through another isotope of thorium, through radium, radon, polonium, bismuth, thallium and lead. The final product is lead-206. The series that starts with thorium-232 ends with lead-208. Soddy was able to isolate the different lead isotopes in high enough purity to demonstrate using chemical techniques that the atomic weights of two samples of lead with identical chemical and spectroscopic properties had different atomic weights. The final picture of these elements reveals that there are several isotopes for each of them. 

When radium (A = 88) emits an alpha particle, its atomic number reduces by 2 and becomes the new element radon (A = 86). The resulting atomic mass is reduced by 4. If th e radium was of the most common isotope, 226, then the radon isotope would have atomic mass number 222. 

A radioactive element is an element that disintegrates spontaneously with the emission of various rays and particles. Most commonly, the term denotes radioactive elements such as radium, radon (emanation), thorium, promethium, uranium, which occupy a definite place in the periodic table because of their atomic number. The term radioactive element is also applied to the various other nuclear species, (which arc produced by the disintegration of radium, uranium, etc.) including (he members of the uranium, actinium, thorium, and neptunium families of radioactive elements, which differ markedly in their stability, and are isotopes of elements from thallium (atomic number 81) to uranium (atomic number... 

Whether in the environment or in the human body, uranium will undergo radioactive decay to form a series of radioactive nuclides that end in a stable isotope of lead (see Chapter 3). Examples of these include radioactive isotopes of the elements thorium, radium, radon, polonium, and lead. Analytical methods with the required sensitivity and accuracy are also available for quantification of these elements in the environment where large sample are normally available (EPA 1980,1984), but not necessarily for the levels from the decay of uranium in the body. More sensitive analytical methods are needed for accurately measuring very low levels of these radionuclides. 

Gilkeson RH, Cowart JB. 1987. Radium radon and uranium isotopes in groundwater from Cambrian-Ordovician sandstone aquifers in Illinois USA. In Graves B, ed. Radon in ground water, radon, radium and other radioactivity in ground water Hydrogeologic impact and application to indoor airborne contamination Proc National Water Well Association conference, Somerset, NJ, April 7-9, 1987. Chelsea, MI Lewis Publishers, Inc., 403-422. 

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. 

The uranium decay series provides the most important isotopes of elements radium, radon, and polonium, which can be isolated in the processing of uranium minerals. Each ton of uranium is associated with 0.340 g of Ra. Freshly isolated Ra reaches radioactive equilibrium with its decay products to Pb in about two weeks (see Fig. 1.2). Many of these products emit energetic y-rays, which resulted in the use of Ra as a y-source in medical treatment of cancer (radiation therapy). However, the medical importance of radium has diminished greatly since the introduction of other radiation sources, and presently the largest use of radium is as small neutron sources (see Table 12.2). 

Advective flux measurements can be conducted using seepage meter, piezometer, dye tracers, and radium or radon isotopes. 

Alpha-emitting radionuclides -including radium- 226, -228, but excluding radon isotopes 0.555 Bq(15pCi)/L... 

Emanometric methods are radioanalytical methods that use measurement of radioactive isotopes of inert gases for the determination of appropriate elements. A good example is the use of the radon isotopes Rn, Rn, and Rn to determine radon, thorium, radium, and actinium. Indirect determinations... 

The noble gases were all discovered during the last decade of the nineteenth century. In 1894, Lord Rayleigh and William Ramsay isolated a new constituent of the air, which they formally called argon in 1895. Helium was first observed in the solar spectrum but was isolated from a uranium mineral by Ramsay in 1895. Krypton, neon, and xenon were obtained by the fractionation of liquid air by Ramsay and Travers in 1898. Rutherford found one radon isotope (Rn-220), the thorium emanation, in 1899, and Dom found another (Rn-222), the radium emanation, in 1900. Ramsay isolated and determined the density of this highly radioactive gas in 1908. 

Twenty isotopes are known. Radon-22, from radium, has a half-life of 3.823 days and is an alpha emitter Radon-220, emanating naturally from thorium and called thoron, has a half-life of 55.6 s and is also an alpha emitter. Radon-219 emanates from actinium and is called actinon. It has a half-life of 3.96 s and is also an alpha emitter. It is estimated that every square mile of soil to a depth of 6 inches contains about 1 g of radium, which releases radon in tiny amounts into the atmosphere. Radon is present in some spring waters, such as those at Hot Springs, Arkansas. 

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-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-degrees G. 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 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

Argon-40 [7440-37-1] is created by the decay of potassium-40. The various isotopes of radon, all having short half-Hves, are formed by the radioactive decay of radium, actinium, and thorium. Krypton and xenon are products of uranium and plutonium fission, and appreciable quantities of both are evolved during the reprocessing of spent fuel elements from nuclear reactors (qv) (see Radioactive tracers). 

Element 86, the final member of the group, is a short-lived, radioactive element, formerly known as radium-emanation or niton or, depending on which radioactive series it originates in (i.e. which isotope) as radon, thoron, or actinon. It was first isolated and studied in 1902 by E. Rutherford and F. Soddy and is now universally known as radon (from radium and the termination-on adopted for the noble gases Latin radius, ray). 

Radioactivity The ability possessed by some natural and synthetic isotopes to undergo nuclear transformation to other isotopes, 513 applications, 516-518 biological effects, 528-529 bombardment reactions, 514-516 diagnostic uses, 516t discovery of, 517 modes of decay, 513-514 nuclear stability and, 29-30 rate of decay, 518-520,531q Radium, 521-522 Radon, 528 Ramsay, William, 190 Random polymer 613-614 Randomness factor, 452-453 Raoult s law A relation between the vapor pressure (P) of a component of a solution and that of the pure component (P°) at the same temperature P — XP°, where X is the mole fraction, 268... 

In 1900 Ernest Rutherford (1871-1937) detected the radon-220 isotope as a decay product of thorium. In the same year, Dorn showed the radon-222 isotope to be a decay product of radium. 

Von Francium ergab sich schon auf Grand der alten Formulierang, daB es kein Liickenelement ist. Tabelle 13 faBt die bei seinen Nachbarelementen Radon und Radium zu erwartenden betastabilen Isotope zu-... 

ISOTOPES There are 37 isotopes of radon. All are radioactive. None are stable. They range in mass numbers from Rn-196 to Rn-228. Their half-lives range from a few microseconds to 3.8235 days for Rn-222, which is the most common. It is a gas that is the result of alpha decay of radium, thorium, or uranium ores and underground rocks. 

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