Radioisotopes Radioactive isotopes

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. 

The isotopes of a particular element have the same number of protons in the nucleus but a different number of neutrons, giving them the same proton number (atomic number) but a different nucleon number (mass number, i.e. number of protons + number of neutrons). Isotopes may be stable or radioactive. Radioactive isotopes (radioisotopes) disintegrate spontaneously at random to yield radiation and a decay product. 

The release of radiation by radioactive isotopes—radioisotopes, for short—is called decay. The nuclei of such radioisotopes are rmstable. However, not aU ruistable nuclei decay in the same way. Some give off more powerful radiation than others or different kinds of radiation. Between 1896 and 1903, scientists had discovered three types of nuclear radiation. Each type changes the nucleus in its own way. These three types were named after the first three letters of the Greek alphabet alpha (a), beta (/3), and gamma (y). 

Radioactive Isotopes (Radioisotopes) For more information about radioisotopes [Americium - 241 (Am-241) Celsium-137 (Cs-137) Cobalt-60 (CO-60) Iodine a-129 1-131) Plutonium-239 (Pu-239) Strontium-90 (Sr-90) Uranium-235 (U-235) and Uranium-238 (U-238)]see the Public Health Statement by the Agency for Toxic Substances and Disease Registry at http //w ww.atsdr.cdc.gov/toxprofiles, or visit the Environmental Protection Agency at littp //www.epa.gov/radiation/radionuclides/americiuni.htni. 

With this nomenclature, the notation 13-A1-27 represents stable aluminum as found in nature. If you look at a Chart of the Nuclides, you will find there are 11 different aluminum isotopes (all are aluminum because they have 13 protons, but they have masses from 23-33 They are all isotopes of aluminum, and all but 13-A1-27 are radioactive isotopes --radioisotopes). Since only aluminum has 13 protons in the nucleus, we often leave the Z value off the notation, such as Al-27. Some of our information sheets have the entries arranged in order of increasing Z, so it is helpful to remember about what the atomic numbers of different elements are to make it easier to find entries in tables. 

It was also discovered that radioactive isotopes (radioisotopes) frequently produce other elements. Rutherford found that radium, for... 

It is not necessary that there be two isotopes in both the sample and the spike. One isotope in the sample needs to be measured, but the spike can have one isotope of the same element that has been produced artificially. The latter is often a long-lived radioisotope. For example, and are radioactive and all occur naturally. The radioactive isotope does not occur naturally but is made artificially by irradiation of Th with neutrons. Since it is commercially available, this last isotope is often used as a spike for isotope-dilution analysis of natural uranium materials by comparison with the most abundant isotope ( U). 

Radiocarbon dating (43) has probably gained the widest general recognition (see Radioisotopes). Developed in the late 1940s, it depends on the formation of the radioactive isotope and its decay, with a half-life of 5730 yr. After forms in the upper stratosphere through nuclear reactions of... 

AH of the 15 plutonium isotopes Hsted in Table 3 are synthetic and radioactive (see Radioisotopes). The lighter isotopes decay mainly by K-electron capture, thereby forming neptunium isotopes. With the exception of mass numbers 237 [15411-93-5] 241 [14119-32-5] and 243, the nine intermediate isotopes, ie, 236—244, are transformed into uranium isotopes by a-decay. The heaviest plutonium isotopes tend to undergo P-decay, thereby forming americium. Detailed reviews of the nuclear properties have been pubUshed (18). 

A radioisotope is an atom the nucleus of which is not stable and which decays to a more stable state by the emission of various radiations. Radioactive isotopes, also called nucHdes or radionucHdes, are important to many areas of scientific research, as well as ia medical and iadustrial appHcations (see... 

The diffusion coefficients of cations in metal oxides are usually measured through the use of radioactive isotopes. Because of the friable nature of oxides it is exU emely difficult to use the sectioning technique employed for metal samples. The need for this can be avoided by the application of radioisotopes which emit radiation having a well established absorption law in matter. Isotopes which emit y radiation are very useful when the cation has a relatively high diffusion coefficient because of the long-range peneU ation of y rays. The absorption law is... 

All radioactive isotopes decay with a characteristic half-life. For example, Fe decays with a half-life of 45 days, while Cu decays with a half-life of 12.6 hours. As a result of the decay, signature high-energy photons or y rays are emitted from a given radioisotope. Thus, Fe emits two prominent y rays at 1099 and 1292 keV, " Na emits at 1368 and 2754 keV, and Zn emits at 1115 keV. Compilations of y rays used in NAA can be found in y-ray tables. 

Radioisotopes are radioactive isotopes. They are used not only to cure disease (as described in Box 17.1), but also to preserve food, to trace mechanisms of reactions, and to power spacecraft. 

Eighteen isotopes of sulfur, 17 of selenium, 21 of tellurium, and 27 of polonium have been registered of these, 4 sulfur, 6 selenium, and 8 tellurium isotopes are stable, while there is no stable isotope of polonium. None of the naturally occurring isotopes of Se is radioactive its radioisotopes are by-products of the nuclear reactor and neutron activation technology. The naturally occurring, stable isotopes of S, Se, and Te are included in Table 1.2. 

Radioisotope—An unstable or radioactive isotope of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified. 

The structure of some isotopes, generally referred to as stable isotopes, is immutable (see Textbox 13). Others, known as radioactive isotopes or radioisotopes, are unstable in time they undergo what is known as... 

Radioactive isotopes that decay by the emission of alpha or beta radiation undergo a change in the nature of their nuclei and are converted into isotopes of other elements. The emission of gamma rays, on the other hand, does not change the nature of the nuclei of the radioisotopes from which the rays are emitted. Gamma rays are a form of dissipation of nuclear energy. 

Tracer studies in which chemically similar species are studied on the basis of containing a radioisotope are discussed in Chapter 10. It is fairly obvious that, with detection techniques readily available for the measurement of non-radioactive isotopes, the principle can be extended to non-radioactive systems. Where in vivo studies are concerned there are clear safety reasons for so doing. Although some progress is being made in this direction, it is... 

Formulating Models Because of safety concerns, it is usually not possible to directly experiment with radioactive isotopes in the classroom. Thus, in this lab, you will use pennies to model the half-life of a typical radioactive isotope. Each penny represents an individual atom of the radioisotope. 

We have considered typical examples of lanthanide and actinide solvent extraction by chelate formation, involving complexes with citric acid and with TTA, to prove that the labelling of a stable element by one of its radioactive isotopes can help to produce accurate data on the stability constants for complex formation. The method is applicable to elements with radioisotopes having a half-life allowing an ion concentration of 10 6m or less. Other methods of partition such as radiopolarography and radio-coulometry also result in accurate thermodynamical data when the same procedure of labelling is used (29). 

ISOTOPES Cs-133 is the only stable isotope of cesium, and it makes up all of the naturally occurring cesium found in the Earth s crust. In addition to Cs-133 there are about 36 radioactive isotopes of Cs, most of which are artificially formed in nuclear reactors. All are produced in small numbers of atoms with relatively short half-lives. The range of Cs isotopes is from Cs-113 (amu = 112.94451) to Cs-148 (amu = 147.94900). Most of these radioisotopes produce beta radiation as they rapidly decay, with the exception of Cs-135, which has a half-life of 3x10 yr, which makes it a useful research tool. Cs-137, with a half-life of 33 years, produces both beta and gamma radiation. 

ISOTOPES There are 27 isotopes of vanadium. Only vanadium-51 is stable and makes up 99.75% of the total vanadium on Earth. The other 0.25% of the vanadium found on Earth is from the radioisotope vanadium-50, which has such a long half-life of 1.4x10+ years that it is considered stable. The other radioactive isotopes have half-lives ranging from 150 nanoseconds to one year. 

ISOTOPES There are 30 isotopes of manganese, ranging from Mn-44 to Mn-69, with only one being stable Mn-55 makes up 100% of the element in the Earth s crust. All the other isotopes are artificially radioactive with half-lives ranging from 70 nanoseconds to 3.7x10 years. Artificial radioisotopes are produced in nuclear reactors, and because most radioactive isotopes are not natural, they do not contribute to the elemenfs natural existence on Earth. 

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. 

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