Radioactivity, natural

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... 

Radioactivity, Natural—The property of radioactivity exhibited by more than 50 naturally occurring radionuclides. 

The preparation of promethium trihalides has been mentioned by Scherer (9). However, the radioactive nature of these compounds has prevented any calorimetric or solubility investigations so far, and they make only one fleeting appearance in this review. 

The radioactive, naturally occurring isotope of potassium——decays by emission... 

The radioactive nature of uranium and associated daughter elements adds an additional dimension to geochemical... 

Since the alpha-ray impacts shattered only a minute proportion of the total number of atoms of boron, aluminum, or magnesium, the chemical identification of the products was extremely difficult. These indefatigable workers, however, accomplished even this. Although it would have been impossible to identify the products simply by ordinary chemical means, the Joliots were able to take advantage of the radioactive nature of the products formed. Since they had good reason to believe that the boron atom had captured a helion and ejected a neutron and that the new element was therefore probably an isotope of nitrogen, they heated some bombarded boron nitride with caustic soda and found that the liberated... 

This enzyme is deficient in Niemann-Pick disease type A/ (Table 4.4.1, Fig. 4.4.1). The assay with radioactive natural substrate is based on the method described by Wenger [59]. The assay with fluorescent substrate is based on the method described by van Diggelen et al. [54]. These assays have not yet been validated in the authors laboratory for use with dried blood spots. For this application the reader is referred to Chamoles et al. [9]. 

Assay Conditions (Assay with Radioactive Natural Substrate)... 

Once again, the periodic table offers clues about which elements could be radioactive naturally. All of the elements in Period 7—like francium in the alkali metals and radium in the alkaline earth metals—are large atoms with many protons. All of the Period 7 elements are radioactive. 

No distinction is made between stable and radioactive naturally occurring isotopes in the table. Of the isotopes included in the table, K40, Rb 7, and Sn124 the 210, 211, 212, and 214 isotopes of Pb and the 210, 211, 212, and 214 isotopes of Bi are radioactive. Likewise, all isotopes of elements beyond bismuth in the Periodic Table are radioactive. 

One of the most common topics asked of those who work with the actinides relates to handling procedures. The radioactive nature of these elements does require the use of special facilities, processes, and precautions. However, working with radioactive elements in subcritical quantities is as safe, if not safer, than handling many of the toxic chemicals found in a typical synthetic laboratory. The primary advantage in handling radioactive material is the ease with which these elements can be detected. Unlike other toxic chemicals, for example, lead, thallium, arsenic, and so on, a simple survey (seconds) with a radiation detector will show if containment of the material has been lost, where it is, and approximately how much is present. With appropriate monitoring, virtually no uptake of radioactive material occurs, and if any personnel contamination does occur, it is quickly detected and treated. 

The radioactive nature of the actinides, especially the transuranics, can introduce significant challenges in the characterization of their complexes. In order to prevent contamination, multiple layers of containment are often required, which can limit the types of studies that can be undertaken. However, a suite of spectroscopic tools has been used to study the chemistry and speciation of the actinides. A partial list of these techniques includes absorption, emission and vibrational spectroscopies, X-ray absorption and diffraction, and multinuclear magnetic resonance. 

All six elements are found in Nature. Radium has no stable isotopes see Isotopes Isotope Labeling), however, Rahas a half-hfe of 1600years. Its decay mode is by a (4.780 MeV) and y emission. As a consequence of this radioactive nature (see Radioactive Decay), its chemistry remains relatively unexplored. In several arenas, rather comprehensive studies have examined various properties of all of the lighter group 2 elements. Efforts have been made to extend all given comparisons to radium however, in some instances this has proven rather difficult. 

PROP A low-melting, volatile, radioactive, naturally occurring metallic element. Mp 254°, bp 962°, d 9.4. 

In the nuclear research centers, the wastes are obtained from research and experimental reactors, hot cells, pilot plants, and decontamination services. These wastes have varying physical, chemical, and radioactive nature due to the great diversity of isotopes used and the wide range of processes in which they are applied. 

The toxicity of plutonium is primarily due to its radioactive nature, and its effects have been extensively studied both in animals and in workers with occupational intakes. Shortly after its discovery in 1941,... 

In most of diese applications, either thoriated tungsten is used (service temperature 1700-1800 °C), or impregnated cathodes, based on Ba0/Al203/Ca0 additions (so-called dispenser cathodes service temperature 900-1250 °C). However, because of its radioactive nature, thoriated tungsten is currently being more and more replaced by timgsten with rare earth (RE) oxide additions or W-Zr02 (see also Section 6.2.2). 

As for their stable analogs, the adsorption of radionuclides may depend on experimental conditions. Any variation results from the chemistry of the element, not form its radioactive nature. For example, the adsorption of the alkali metal cesium is largely independent of pH, whereas pH dependence is to be expected for oxyanions (Chapter 5, this volume) such as selenite and selenate and for transition metals such as nickel, silver, and palladium. 

The compounds of thorium find extensive use on account of their radioactive nature. 

Second, the radioactive nature of the product imposes handling difficulties in performing the test, since quality control departments may not have the necessary facilities for handling radioactive materials, and radiopharmacy departments may not be suitably equipped to perform sterility testing. 

Radioactive Natural sources, mining of ra-substances dioactive ores, fission processes, nuclear experiments... 

Two crystalline modifications of polonium exist at atmospheric pressure—the low temperature -cubic form and the high temperature )3-rhom-bohedral form (30). The a to transition occurs between 75° and 100°C however, the to a transition is observed at about 10°C thus the equilibrium temperature for the transition has not been established. Polonium has been diflBcult to study because of its radioactive nature and its decay into lead. 

Owing to the toxic and radioactive nature of uranium compounds, there must be excellent ventilation facilities for FAES or FAAS. 

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