Isotope naturally radioactive

Frisch, O. R. 1958. The Nuclear Handbook. Princeton, NJ Van Nostrand. This book is intended as a desk reference source for those interested in the science and technology of nuclear physics. Material is presented in a concise format. Topics covered include radiation effects and protection, elements and isotopes, natural radioactivity, nuclear materials, particle accelerators, and nuclear reactors. 

Neutron Activation Analysis Few samples of interest are naturally radioactive. For many elements, however, radioactivity may be induced by irradiating the sample with neutrons in a process called neutron activation analysis (NAA). The radioactive element formed by neutron activation decays to a stable isotope by emitting gamma rays and, if necessary, other nuclear particles. The rate of gamma-ray emission is proportional to the analyte s initial concentration in the sample. For example, when a sample containing nonradioactive 13AI is placed in a nuclear reactor and irradiated with neutrons, the following nuclear reaction results. 

Radiochemical methods of analysis take advantage of the decay of radioactive isotopes. A direct measurement of the rate at which a radioactive isotope decays may be used to determine its concentration in a sample. For analytes that are not naturally radioactive, neutron activation often can be used to induce radioactivity. Isotope dilution, in which a radioactively labeled form of an analyte is spiked into the sample, can be used as an internal standard for quantitative work. 

Natural radioactive processes in themselves give rise to changes of one element into another. Emission of an alpha particle reduces the atomic number of an element by two units, and emission of a beta particle increases the atomic number by one unit. Thus, for isotopes of elements near... 

A few natural isotopes are radioactive. Of the three isotopes of hydrogen, only that of mass 3 (tritium) i.s radioactive. Radioactive isotopes can be examined by other instrumental means than mass spectrometry, but these other means cannot see the nonradioactive isotopes and are not as versatile as a mass Spectrometer. 

Lead, atomic number 82, is a member of Group 14 (IVA) of the Periodic Table. Ordinary lead is bluish grey and is a mixture of isotopes of mass number 204 (15%), 206 (23.6%), 207 (22.6%), and 208 (52.3%). The average atomic weight of lead from different origins may vary as much as 0.04 units. The stable isotopes are products of decay of three naturally radioactive elements (see Radioactivity, natural) comes from the uranium series (see Uraniumand... 

Rhenium, atomic wt 186.2, occurs in nature as two nucHdes Re [14391-28-7] mass 184.9530, in 37.500% abundance and Re [14391-29-8], mass 186.9560, in 62.500% abundance. The latter isotope is radioactive, emitting very low energy radiation and having a half-life estimated at 4.3 ( 0.5) X 10 ° yr. The radioactive decay of this isotope has been used to date accurately the time of Earth s formation. 

Hydrogen as it occurs in nature is predominantly composed of atoms in which the nucleus is a single proton. In addition, terrestrial hydrogen contains about 0.0156% of deuterium atoms in which the nucleus also contains a neutron, and this is the reason for its variable atomic weight (p. 17). Addition of a second neutron induces instability and tritium is radioactive, emitting low-energy particles with a half-life of 12.33 y. Some characteristic properties of these 3 atoms are given in Table 3.1, and their implications for stable isotope studies, radioactive tracer studies, and nmr spectroscopy are obvious. 

Lead (13 ppm) is by far the most abundant of the heavy elements, being approached amongst these only by thallium (8.1 ppm) and uranium (2.3 ppm). This abundance is related to the fact that 3 of the 4 naturally occurring isotopes of lead (206, 207 and 208) arise primarily as the stable end products of the natural radioactive series. Only (1.4%)... 

Polonium has no stable isotopes, all 27 isotopes being radioactive of these only °Po occurs naturally, as the penultimate member of the radium decay series ... 

Promethium (Z = 61) is essentially nonexistent in nature all of its isotopes are radioactive. Write balanced nuclear equations for the decomposition of... 

Radioactivity. Methods based on the measurement of radioactivity belong to the realm of radiochemistry and may involve measurement of the intensity of the radiation from a naturally radioactive material measurement of induced radioactivity arising from exposure of the sample under investigation to a neutron source (activation analysis) or the application of what is known as the isotope dilution technique. 

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. 

Americium (pronounced,, am-8- ris(h)-e-8m) is a man-made, radioactive, actinide element with an atomic number of 95. It was discovered in 1945. Actinides are the 15 elements, all of whose isotopes are radioactive starting with actinium (atomic number 89), and extending to lawrencium (atomic number 103). When not combined with other elements, americium is a silvery metal. Americium has no naturally occurring or stable isotopes. There are two important isotopes of... 

Neutron activation analysis (NAA) is a technique for the qualitative and/or quantitative determination of atoms possessing certain types of nuclei. Bombarding a sample with neutrons transforms some stable isotopes into radioactive isotopes measuring the energy and/or intensity of the gamma rays emitted from the radioactive isotopes created as a result of the irradiation reveals information on the nature of the elements in the sample. NAA Is widely used to characterize such archaeological materials as pottery, obsidian, chert, basalt, and limestone (Keisch 2003). 

Not all of the nuclei of a given sample of a radioactive isotope disintegrate at the same time the nuclei disintegrate over a period of time. The number of radioactive disintegrations per unit time that occur in a given sample of a naturally radioactive isotope is directly proportional to the quantity of that isotope present. The more nuclei present, the more will disintegrate per second (or per year, etc.). 

Rn-220 is another isotope of radon and belongs to the thorium decay series. Due to its short half life of 55.6 s, reports on its concentrations in those gases and in natural water are still scant. They are also important for a better estimate of our exposure to natural radioactivity and also for the geochemical study of the forma tion of those radon isotopes and their underground movement. 

Although many nuclei are naturally radioactive, there are three main radioactive series in nature, all of which are relevant to a discussion of the isotopic composition of natural lead. These start with the elements uranium and thorium (238U, 235U and 232Th) and all end in one of the three stable isotopes... 

The number of protons is unique to the element but most elements can exist with two or more different numbers of neutrons in their nucleus, giving rise to different isotopes of the same element. Some isotopes are stable, but some (numerically the majority) have nuclei which change spontaneously - that is, they are radioactive. Following the discovery of naturally radioactive isotopes around 1900 (see Section 10.3) it was soon found that many elements could be artificially induced to become radioactive by irradiating with neutrons (activation analysis). This observation led to the development of a precise and sensitive method for chemical analysis. 

The Development of Modern Chemistry. Harper and Row, New York, 1964, xii + 851 pp. including illustrations, Appendixes, (Discovery of the Elements, Discovery of Natural Radioactive Isotopes, Radioactive Decay Series, Nobel Prize Winners in Chemistry, Physics, and Medicine), and Bibliographic Notes. 

Choosing a method to determine isotope effects on rate constants, and selecting a particular set of techniques and instrumentation, will very much depend on the rate and kind of reaction to be studied, (i.e. does the reaction occur in the gas, liquid, or solid phase , is it 1st or 2nd order , fast or slow , very fast or very slow , etc.), as well as on the kind and position of the isotopic label, the level of enrichment (which may vary from trace amounts, through natural abundance, to full isotopic substitution). Also, does the isotopic substitution employ stable isotopes or radioactive ones, etc. With such a variety of possibilities it is useless to attempt to generate methods that apply to all reactions. Instead we will resort to discussing a few examples of commonly encountered strategies used to study kinetic isotope effects. 

ISOTOPES There are 29 isotopes of strontium, ranging from Sr-75 to Sr-102. The four natural forms of strontium are stable and not radioactive. These stable isotopes are Sr-84, which constitutes 0.56% of the elemenfs existence on Earth Sr-86, which makes up 9.86% Sr-87, which accounts for 7.00% of the total and Sr-88, which makes up 82.58% of strontium found on Earth. The remaining isotopes are radioactive with half-lives ranging from a few microseconds to minutes, hours, days, or years. Most, but not all, are produced in nuclear reactors or nuclear explosions. Two important radioisotopes are Sr-89 and Sr-90. 

ISOTOPES There are 28 isotopes of scandium, ranging from scandium-36 to scandium-57. Scandium-45 is the only stable isotope and contains about 100% of the natural scandium found in the Earth s crust. The remaining isotopes are radioactive with half-lives ranging from nanoseconds to a few minutes to a few hours to a few days, and therefore, they are not found naturally in the Earth s crust. The radioactive isotopes of scandium are produced in nuclear reactors. 

ISOTOPES There are 30 isotopes of iron ranging from Fe-45 to Fe-72. The following are the four stable isotopes with the percentage of their contribution to the elemenfs natural existence on Earth Fe-54 = 5.845%, Fe-56 = 91.72%, Fe-57 = 2.2%, and Fe-58 = 0.28%. It might be noted that Fe-54 is radioactive but is considered stable because it has such a long half-life (3.1 xlO years). The other isotopes are radioactive and are produced artificially. Their half-lives range from 150 nanoseconds to 1x10 years. 

ISOTOPES There are 33 Isotopes of cobalt, ranging from Co-48 to Co-75, with half-lives ranging from a few nanoseconds to 5.272 years for cobalt-60. Cobalt-59 Is the only stable Isotope that constitutes almost all (roughly 100%) of the element s natural presence on Earth. All the other Isotopes are radioactive and are created artificially in nuclear reactors or nuclear explosions. 

ISOTOPES There are 38 isotopes of zinc, ranging in atomic weights from Zn-54 to Zn-83. Just four of these are stable, and those four, plus one naturally radioactive isotope (Zn-70) that has a very long half-life (5x10+ years), make up the element s existence on Earth. Their proportional contributions to the natural existence of zinc on Earth are as such Zn-64 = 48.63%, Zn-66 = 27.90%, Zn-67 = 4.10%, Zn- 68 = 18.75%, and Zn-70 = 0.62%. All the other isotopes are radioactive and artificially produced. 

ISOTOPES Zirconium has 37 isotopes, ranging from Zr-79 to Zr-110. Four of them are stable, and one is a naturally radioactive isotope, with a very long half-life. All five contribute to the element s natural existence on Earth. The stable isotopes are the following Zr-90 = 1.45%, Zr-91 = 11.22%, Zr-92 = 17.15%, and Zr-94 = 17.38%. The one natural radioactive isotope is considered stable Zr-96, with a half-life of 2.2 x 10+ years, contributes 2.80% to zirconium s total existence on Earth. All of the other isotopes are artificially radioactive and are produced in nuclear reactors or particle accelerators. They have half-lives ranging from 150 nanoseconds to 1.53 x 10+ years. 

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