Isotope uranium family

A decisive role in further developments was played by the radioelement UY, a thorium isotope discovered in 1911 by the Russian radiochemist G. Antonov who worked in Rutherford s laboratory. The radioelement UXi (also a thorium isotope) in the uranium family emits beta particles and gives rise to brevium (UXg). 

The mass numbers of all isotopes in the family of thori-um-232 are divided by four. Therefore, the thorium family is sometimes referred to as the 4re family. After division by four of the mass numbers of the isotopes in the two uranium families we get a remainder of two or three. Respectively, the uranium-238 family is known as the (4re + 2) family and the uranium-235 family as the (4re + 3) family. 

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

The first member of this family, manganese, exhibits One of the most interesting redox chemistries known thus it has already been discussed in detail above. Technetium exhibits the expected oxidation states, and associated with these are modest emf values. All of the isotopes of technetium are radioactive but "Tc has a relatively long half-life (2.14 k 10s years) and is found in nature in small amounts because of the radioactive decay of uranium. Oxidation slates of rhenium range from +7 to - 3, with some species ReOj and Re3+) unstable with respect to disproportionation. 

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... 

The natural radioelements are listed in Table 14.1. Isotopes of these elements are members of the uranium, actinium and thorium families (Table 1.2, and Tables 4.1 to 4.3). In the ores of U and Th the concentrations of natural radioelements are relatively high and proportional to the half-life. The average concentration of U in the earth s crust is about 2.9 mg/kg (ppm) and that of Th about 11 mg/kg (ppm). The... 

The half life of a radioactive element is the time it takes for half of a sample of the element to break down. That means that 10 grams of the isotope they studied would break down very quickly. Only 5 grams would be left after 1.175 minutes. Then 2.5 grams (half of 5 grams) would be left after another 1.175 minutes, and 1.25 grams (half of 2.5 grams) after another 1.175 minutes, and so on. Until the discovery by Fajans and Gohring, the element had been known as uranium-X2. That name came from the element s position in one of the radioactive families. 

The displacement law provided for harmonious relationship between radioactive families and the periodic system of elements. After several successive alpha and beta decays the originators of the families converted into stable lead giving rise in the process to the natural radioactive elements found between uranium and bismuth in the periodic table. But then each box in the system had to accommodate several radioelements. They had identical nuclear charges but different masses, that is, they looked as varieties of a given element with identical chemical properties but different masses and radioactive characteristics. In December 1913 Soddy suggested the name isotopes for such varieties of elements (from the Greek for the common place ) because they occupy the same box in the periodic system. 

Now it is clear that radioelements are just isotopes of natural radioactive elements. The three emanations are the isotopes of the radioactive element radon, the number 86 in the periodic system. The radioactive families consist of the isotopes of uranium, thorium, polonium, and actinium. Later many stable elements were found to have isotopes. An interesting observation may be made here. When a stable element was discovered this meant simultaneous discovery of all its isotopes. But in the cases of natural radioactive elements individual isotopes were discovered first. The discovery of radioelements was the discovery of isotopes. This was a significant difference between stable and radioactive elements in connection with the search for them in nature. No wonder that the periodic system was badly strained when accommodation had to be found for the multitude of radioelements,—it was a classification of elements, after all, not isotopes. The discovery of the displacement law and isotopy greatly clarified the situation and paved the way for future advances. 

The French scientist A. Picard in 1917 suggested that a similar situation had to prevail at the origin of the family which was still known as the actinium family. His idea, which was confirmed only much later, was that the originator of this family was a third, still unknown uranium isotope... 

The natural isotopes of uranium and thorium in long series of successive radioactive transformations give rise to secondary chemical elements. In the first decade of the 20th century scientists had in their disposal about forty radioactive isotopes of the elements at the end of the periodic system, that is, from bismuth to uranium. These radioelements comprised three radioactive families headed by thorium-232, uranium-235 and uranium-238. Each radioactive element sent, its representatives to these families with the only exception of eka-iodine and eka-cesium. None of the three series had links that would correspond to the isotopes of element 85 or 87. This suggested an unexpected idea that eka-iodine and eka-cesium were not radioactive. But why Nobody dared to answer this question. Under this assumption it was meaningless to look for these elements in the ores of uranium and thorium which contained all the radioactive elements without exception. 

Just a year later three radiochemists from Vienna— S. Meyer, G. Hess, and F. Paneth—studied actinium-227, an isotope belonging to the family of uranium-235. They repeated their experiments and at last their sensitive instruments detected alpha particles of unknown origin. Alpha particles emitted by various isotopes have specific mean paths in air (of the order of a few centimetres). The mean path of the alpha particles in the experiments of the Austrian scientists was 3.5 cm. No known alpha-active isotope had such mean path of alpha particles. The scientists from the Vienna Radium Institute concluded that these particles were the product of alpha decay of the typically beta-active actinium-227. A product of this decay had to be an isotope of element 87. 

In the comprehensive studies of the radioactive species produced in the fission of uranium it has been found that over thirty are members of the rare earth family (isotopes of yttrium and the group lanthanum through europium). The chemical and physical identification of these was an important part of the research program of the Manhattan Project. Standard oxidative separations and fractional precipitations and the use of radiochemical methods based on chain relations served to distinguish the activities of yttrium, lanthanum, cerium, and some of praseodymium, and those of samarium and europium. The characterization of the sequence praseodymium, neodymium, and element 61 presented very difficult problems that were solved only with the intensification of ion exchange methods originally developed by Boyd and co-workers and applied to the rare earth field by Cohn and co-workers. (Marinsky et al. 1947)... 

Uranium, element 92, is a member of the actinide family of the periodic table, which includes elements 89-104. It has 3 primordial and 12 artificial or man-made isotopes, all of which are radioactive. The naturally occurring uranium series is headed by which subsequently decays... 

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