Nuclear chemistry - part of high-energy chemistry , a branch of physical chemistry - studies nuclear reactions and the accompanying physical and chemical processes, establishes the relationship between the physical, chemical and nuclear properties of a substance. Often, nuclear chemistry means areas of research in radiochemistry (sometimes as a division of it) and radiation chemistry . These are different sciences, but nuclear chemistry is a theoretical foundation for them. The term nuclear chemistry, even at present, is not universally accepted due to the fact that the conversion of atomic nuclei is initially a field of nuclear physics , and chemistry, by definition, studies only chemical reactions in which atomic nuclei remain unchanged. Nuclear chemistry originated at the intersection of radiochemistry , chemical physics and nuclear physics
Content
History
The nucleation of nuclear chemistry, as well as nuclear physics , is associated with the discovery of the radioactivity of uranium (A. Beckerel, 1896), Th and its decay products - new, radioactive elements Ro and Ra (M. Sklodowska-Curie and P. Curie, 1898). Further development was determined by the discovery of the arts. nuclear transformation (E. Rutherford, 1919), isomerism of atomic nuclei of natural radionuclides ( Otto Gan , 1921), and isomerism of art. atomic nuclei (I.V. Kurchatov et al., 1935), fission of U nuclei under the influence of neutrons (O. Gan, F. Strassman, 1938), spontaneous fission of U (G. N. Flerov and K. A. Petrzhak, 1940 ) The creation of nuclear reactors (E. Fermi, 1942) and particle accelerators (J. Cockcroft and E. Walton, 1932) made it possible to study the processes occurring in the interaction of high-energy particles with complex nuclei and made it possible to synthesize artificial radionuclides and new elements. The development of nuclear chemistry as a science is connected with the work of the American chemist and nuclear physicist (nuclear chemist) Glenn Seborg during the creation of the atomic bomb. Nuclear chemistry was designed to solve the problem of obtaining weighted amounts of plutonium . Modern nuclear chemistry was formed thanks to the emergence of a new field of physical chemistry - high energy chemistry .
The main directions of nuclear chemistry
- study of nuclear reactions and related physical and chemical processes;
- chemistry of "new atoms";
- search and synthesis of new elements and radionuclides by the reactor method;
- search for new types of radioactive decay.
Nuclear chemistry methods
To solve the problems posed in nuclear chemistry, radiochemical, ionization, and, more recently, mass spectrometric methods are used, and thick-layer photoemulsions are also used. The most important task of nuclear chemistry is the isolation and identification of nuclear reaction products by radiochemical methods. These methods play a special role in the study of nuclear reactions in which a complex mixture of nuclides of various elements is formed. To isolate them, radiochemical variants of precipitation, extraction, ion-exchange chromatography, electrolysis and distillation methods are used. Nuclides are identified by the nature of the radiation, by measuring energy and half-life, or by mass spectrometry. For this purpose, multi-channel spectrometers and various types of counters are used. Studying the mechanism of nuclear transformations made it possible to understand the processes taking place in space, the origin and distribution of chemical elements, explain the anomalies in the isotopic composition of various natural objects, obtain radioactive isotopes of almost all chemical elements and synthesize new elements of the periodic system, including actinides and transactinoids. To determine the half-life of short-lived nuclides (T1 / 2 <1 min), a special technique is used to measure the lifetime of the nuclide from the moment of its formation to decay directly on the detector.
Problems of Nuclear Chemistry
Some radiochemical problems are sometimes referred to nuclear chemistry, for example, the study of the chemistry of “hot atoms” arising from various nuclear transformations. As a result of radioactive decay, hot atoms have excess (compared to ordinary medium atoms) kinetic energy formally corresponding to temperatures of 10,000-10,000,000 K and exceeding the activation energy of many chemical reactions. In collisions with atoms and molecules of the medium, hot atoms are able to stabilize in compounds other than the original ones (Sildard – Chalmers effect; 1934). This effect is used in radiochemistry to study the mechanism of reactions of hot atoms with the medium, for the synthesis of labeled compounds, the separation of isotopes, etc.
Using the methods of nuclear chemistry using "new atoms", and especially positronium (Ps) and muonium (Mu), we study atomic transformations in various chemical systems - meson chemistry .
Literature
- Friedlander G., Kennedy J., Miller J., Nuclear chemistry and radiochemistry, trans. from English., M., 1967;
- Choppin G., Rydberg Y., Nuclear chemistry. Fundamentals of theory and application, trans. from English., M., 1984;
- Chemical Encyclopedia, 1985;
- Modern Nuclear Chemistry by Walter D. Loveland