Radioactive isotopes technetium

I don t say that they should change from basic research to applied research they still may be carrying on the basic research, but they need to explain to the public the importance of it. So many things are discovered. For example, in the case of my discovery of all these radioactive isotopes — technetium-99m, iodine-131, cobalt-60, and cesium-137, all turned out to have tremendous practical applications in nuclear medicine. There are millions of applications per year now. 

One radioactive isotope of molybdenum is commonly used in medicine, molybdenum-99m. (The m in this instance stands for metastable, which means the isotope does not last very long.) This isotope is not used directly, however. Instead, it is used in hospitals to make another radioactive isotope, technetium-99m. This isotope of technetium (atomic number 43) is widely used as a tracer for diagnostic studies of the brain, liver, spleen, heart, and other organs and body systems. 

Several modes of waste management are available. The simplest is to dilute and disperse. This practice is adequate for the release of small amounts of radioactive material to the atmosphere or to a large body of water. Noble gases and slightly contaminated water from reactor operation are eligible for such treatment. A second technique is to hold the material for decay. This is appHcable to radionucHdes of short half-life such as the medical isotope technetium-9 9m = 6 h), the concentration of which becomes negligible in a week s holding period. The third and most common approach to waste... 

All isotopes of technetium (Z = 43) are unstable, so the element is not found an Avhere in the Earth s crust. Its absence left a gap in the periodic table below manganese. The search for this missing element occupied researchers for many years. It was not until 1937 that the first samples of technetium were prepared in a nuclear reactor. In fact, technetium was the first element to be made artificially in the laboratory. To date, 21 radioactive isotopes of technetium have been identified, some of them requiring millions of years to decompose. 

C22-0008. There are no stable isotopes of technetium, but several radioactive isotopes can be prepared. 

Metal-metal (M-M) bonds, first noted in the early sixties, occur in several thousand transition-metal compounds [1]. Complex technetium compounds and compounds with M-M bonds (clusters) have been studied more extensively than many other classes of inorganic compounds. Increasing interest in technetium compounds is due to the practical uses of the "mTc isotope, which ranks first among radioactive isotopes used in nuclear medicine diagnostics [2-4]. On the other hand, technetium clusters are an interesting object for theoretical studies, because until recently, they were the only compounds in which the presence of these anomalous chemical bonds was thought possible. 

Iodine-131 was among the first radioactive isotopes used for radioimmunoconjugate preparation (Order, 1982 Regoeczi, 1984). Since the earliest studies on the efficacy of radiotherapy, additional isotopes have been employed, such as iodine-125, bismuth-212, yttrium-90, yttrium-88, technetium-99 m, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-111, indium-114 m, indium-115, and boron-10. 

Table A. 1 comprises the stable elements from hydrogen to bismuth with the radioactive elements technetium and promethium omitted. Natural variations in isotopic composition of some elements such as carbon or lead do not allow for more accurate values, a fact also reflected in the accuracy of their relative atomic mass. However, exact masses of the isotopes are not affected by varying abundances. The isotopic masses listed may differ up to some 10 u in other publications.

The most sensitive method for determining trace amounts of technetium is the neutron activation . The Tc sample is irradiated by slow neutrons. The radioactive isotope Tc with a half-life of 15.8 s is formed by the reaction Tcfn, y) Tc, the neutron capture cross section of which is comparatively large (20 bams), so that it is possible to determine amounts < 2x 10 " g of Tc. However, the method is not widely used since the half-life of Tc is very short. Moreover, this method is only convenient when a reactor or a neutron source is available. 

ISOTOPES There are 47 isotopes. None are stable and all are radioactive. Most are produced artificially in cyclotrons (particle accelerators) and nuclear reactors. The atomic mass of its isotopes ranges from Tc-85 to Tc-118. Most of technetium s radioactive isotopes have very short half-lives. The two natural radioisotopes with the longest half-lives—Tc-98 = 4.2x10+ years and Tc-99 = 2.111 xl0+ years—are used to establish technetium s atomic weight. 

The major characteristic of technetium is that it is the only element within the 29 transition metal-to-nonmetal elements that is artificially produced as a uranium-fission product in nuclear power plants. It is also the tightest (in atomic weight) of all elements with no stable isotopes. Since all of technetiums isotopes emit harmful radiation, they are stored for some time before being processed by solvent extraction and ion-exchange techniques. The two long-lived radioactive isotopes, Tc-98 and Tc-99, are relatively safe to handle in a well-equipped laboratory. 

Recovery of technetium, present as pertechnetate in aqueous acidic solution, is of utmost importance because of its long half-life of 2.13 x 105 years and its relative mobility in the environment. The close relation between TCO4 and the isoelectronic perrhenate Re04 makes the latter a widely used model for artificially produced technetium, which only possesses radioactive isotopes. 

Elements with atomic numbers ranging from 90 to 103, the actinides, are members of a transition series in which the first member is actinum (atomic number 89). They are analogues to lanthanides and occupy the same part of the Periodic Table at the next period. Only four of them have been found in nature the others are manmade elements produced by neutron irradiation or heavy-ion bombardment. All of them are radioactive [282]. Technetium (element 43), although not part of the actinides series, possesses two radioactive isotopes with long half-lives "Tc (2.12 x 105s, has the practical use) and 98Tc (1.5 x 106 years, a rhenium analogue) [283],... 

The first element ever to be produced artificially is that of atomic number 43. In 1937, Perrier and Segre isolated minute amounts of a radioactive isotope of this element from a sample of molybdenum that had been bombarded with deuterons in a cyclotron. This element was given the name technetium (Tc), which is derived from the Greek word meaning artificial. The bulk of the evidence now available indicates that this element does not occur in nature. Although several isotopes of... 

Some hazardous metals such as chromium (Cr) and radioactive fission products such as technetium (Tc) exhibit exactly opposite solubility characteristics as compared to the metals discussed above. These metals in higher oxidation states, e.g., chromates (Cr ) and pertechnetate (Tc ), are more soluble than their counterparts, e.g., chromium and technetium oxide (Cr and Tc " "). Chromium is a hazardous metal and technetium ( Tc) is a radioactive isotope. As we shall see in Chapters 16 and 17, one way to reduce their dispersibility is to reduce their solubility in ground water and reduce them into their lower oxidation state, and then encapsulate them in the phosphate ceramic. Thus, the reduction approach is also useful in stabilization of hazardous metal oxides of high oxidation states. Because of these reasons, a good understanding of the reduction mechanism of oxides... 

A radioactive isotope (radioisotope) is an unstable isotope of an element that decays into a more stable isotope of the same element. They are of great use in medicine as tracers (to help monitor particular atoms in chemical and biological reactions) for the purpose of diagnosis (such as imaging) and treatment. Iodine (-131 and -123) and Technetium-99 are used for their short half-lives. 

All the possible mass numbers between 142 and 150 are already taken by neod)Tnium (Z = 60) and samarium (Z = 62), so that no stable isotope is expected for element 61. They would all be radioactive, just as in the case of technetium (Z = 43). The Mattauch rule however was not capable of ascribing these radioactive isotopes a certain half-life. A number of uranium and thorium isotopes are also radioactive, but their half-lives are great enough so that one can still find them in nature. During that same year, in 1934, the American physicist and future Noble Prize winner, Willard Libby (1908-1980), discovered that neodymium is a (3 emitter (Libby, 1934). According to Soddy s displacement laws, this should imply that when neodymium decays, isotopes of element 61 should be formed. 

Technetium. No stable isotopes of element 43 exist. Minute amounts of radioactive isotopes have been made, by Segre and his collaborators, who have named the element technetium, symbol Tc. 

Nuclear chemistry (radiochemistry) has now become a large and very important branch of science. Over four hundred radioactive isotopes have been made in the laboratory, whereas only about three hundred stable isotopes have been detected in nature. Three elements —technetium (43), astatine (85), and promethium (61), as well as some trans-uranium elements, seem not to occur in nature, and are available only as products of artificial transmutation. The use of radioactive isotopes as tracers has become a valuable technique in scientific and medical research. The controlled release of nuclear energy promises to lead us into a new world, in which the achievement of man is no longer limited by the supply of energy available to him. 

Molybdenum-99 is a radioactive isotope that decays to form technetium-99m, an isotope used in about 36,000 medical procedures each day in the United States. Technetium-99m allows physicians to diagnose many conditions in the brain, lungs. 

All 37 isotopes of technetium are radioactive. The most stable of these isotopes, technetium-97 and technetium-98, have half lives of 2.6 million years and 4.2 million years, respectively. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. 

The radioactive isotope most widely used in nuclear medicine is tech-netium-99, which has a short half-life and emits low-energy gamma rays. This radioactive isotope is used in bone scans. Bone repairs occur when there is a fracture, infection, arthritis, or an invading cancer. Bones that are repairing themselves take in minerals and absorb the technetium at the same time. If an area of bone has an unusual amount of repair, the technetium will gather there. Cameras detect the gamma rays that result from its decay. 

Technetium is one of the most nsefnl elements in nnclear medicine. Although technetium is a transition metal, all its isotopes are radioactive. Therefore, technetium does not occur naturally on Earth. In the laboratory it is prepared by the nuclear reactions... 

Radioactive molybdenum-99 is used to produce the tracer isotope, technetium-99m. Write a nuclear equation for the formation of molybdenum-99 from stable molybdenum-98 bombarded with neutrons. 

Peacock RD (1966) The chemistry of technetium and rhenium. Elsevier, London Perrier C, Segre E (1937) Radioactive isotopes of element 43. Nature 140 193-194 Perrier C, Segre E (1947) Technetium the element of atomic munber 43. Natiu"e 159 24 (Letter) Richards P (1966) Nuclide generators. In Radioactive pharmaceuticals. USAEC symposiiun series, no. 6, (CONF-651111), Oak Ridge, Term., pp 155-163 Rimmer J (1982) Radiopharmaceutical composition based on technetium-99m and the reagent for making it. Eur Patent Appl EP 78,642... 

Klement 43 in the seventh subgroup of the periodic system, technetium, is the lowest atomic number radioelement. Stable, non-radioactive isotopes do not exist according to Mattauch s rule. Technetium isotopes can be produced artificially by nuclear processes. Long-lived isotopes are Tc (2.6 10 a), Tc (4.2 10 a) and Tc (2.1 10- a). The spectroscopic discovery of technetium in several fixed stars provided the first proof of stellar synthesis of heavy nuclides. Traces of Tc occur in the earth s crust where they arise mainly from spontaneous fission of... 

All atomic mass numbers from 1 to 238 are found naturally on earth except for masses 5 and 8. About 285 relatively stable and 67 naturally radioactive isotopes occur on earth totaling 352. In addition, the neutron, technetium, promethium, and the transuranic elements (lying beyond uranium) have now been produced artificially. In June 1999, scientists at the Lawrence Berkeley National Laboratory reported that they had found evidence of an isotope of Element 118 and its immediate decay... 

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