Radioactive isotopes discovery

The number of protons is unique to the element but most elements can exist with two or more different numbers of neutrons in their nucleus, giving rise to different isotopes of the same element. Some isotopes are stable, but some (numerically the majority) have nuclei which change spontaneously - that is, they are radioactive. Following the discovery of naturally radioactive isotopes around 1900 (see Section 10.3) it was soon found that many elements could be artificially induced to become radioactive by irradiating with neutrons (activation analysis). This observation led to the development of a precise and sensitive method for chemical analysis. 

The Development of Modern Chemistry. Harper and Row, New York, 1964, xii + 851 pp. including illustrations, Appendixes, (Discovery of the Elements, Discovery of Natural Radioactive Isotopes, Radioactive Decay Series, Nobel Prize Winners in Chemistry, Physics, and Medicine), and Bibliographic Notes. 

In 1898 there was discovered an element, radium, which con tinually and spontaneously emits light, heat, and other radiations. Investigation of these astonishing phenomena by the Curies and others revealed more than forty interrelated radioactive elements which, like radium, are unstable. They do not, however, occupy forty places in the periodic system, but are crowded into twelve places. The explanation for the existence of these numerous so-called radioactive isotopes and their genealogical descent from uranium and thorium were discovered independently by K. Fajans, F. Soddy, A. S. Russell, and A. Fleck. Since the original literature on the radioactive elements embraces such a vast field of research, the following account of their discovery is necessarily far from complete. 

Sir Alexander Fleck, 1889—. Author of many research papers on the radioactive isotopes. He proved the inseparability of uranium Xi and radioaetinium from thorium, of thorium B and actinium B from lead, of mesothorium 2 from actinium, of radium E from bismuth, and of radium A from polonium, and confirmed the discovery of uranium X3 by Faj ans and O. H. Gohring. Chairman of Imperial Chemical Industries, Ltd. See also ref. (1S7). 

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. 

Various authorities list slightly different isotopes for some elements. One reason is that the discovery of a new isotope may not yet have been confirmed by other researchers, so its existence is uncertain. Lists of isotopes may change also because new isotopes are being discovered from time to time. The number of isotopes, with a known half life, listed in this book is based on information available from the Lawrence Berkeley National Laboratory in Berkeley, California. The list is up to date as of December 2009. All stable isotopes exist in nature. Some radioactive isotopes also exist in nature, but the vast majority has been prepared synthetically in the laboratory. 

Becquerel s discovery led other researchers, including Marie and Pierre Curie, to discover and study new radioactive elements. Many radioactive isotopes, or radioisotopes, now have important medical, agricultural, and industrial uses. 

The radioactive isotope 26Al decays to 26Mg with a very short half-life of 7.2 X 105 years, and so 26Al becomes extinct within a few million years of its formation. Some have likened this isotope system to the second-hand on the clock of the Universe. 26Al was produced by explosions in supernovae early in the history of the Universe. The discovery of the excesses of the daughter isotope 26Mg in very early solar system objects such as CAIs indicates that they contained 26Al at the time of their formation and so must have formed within a very short time of the supernova explosion (see Section 2.3.3.2). 

The understanding of radioactivity has grown rapidly in the 100 years since its discovery. When the Curies worked with radioisotopes, they did not realize how harmful such materials could be. Marie Curie died of leukemia that was probably caused by her years of contact with radioisotopes. Many more radioactive isotopes exist than the few studied by the Curies. In fact, most of the roughly 2000 known isotopes of all elements are unstable and rmdergo nuclear decay. Fortrmately, most of those do not occur naturally, but are produced synthetically. Your surroundings contain mostly stable isotopes of the common elements, so you are not normally exposed to enough radiation to do you much harm. 

Scientists are continuing to search for new chemical species in the interstellar medium. Sometimes that search is simply an effort to learn more about the chemical composition of the ISM, but in other cases, the discovery of a particular chemical species can yield useful information about the evolution of the universe itself. For example, some research teams have been especially interested in determining the distribution of the radioactive isotope aluminum-26 in the ISM. The reason for their interest is that aluminum-26 is produced during certain element-forming reactions in stars. Its presence can... 

However, subsequent work—especially the discovery of nuclear fission by Otto Hahn and F. S. Strassmann and their coworkers in 1938—showed that the interpretation of Fermi and Segr was not correct. It revealed that radioactive products of the Fermi-Segrd experiments were actually radioactive isotopes of lighter elements, fission products like iodine or tin. 

A chemist proposes a research project to discover a catalyst that will speed up the decay of radioactive isotopes that are waste products of a medical laboratory. Such a discovery would be a potential solution to the problem of nuclear waste disposal. Critique this proposal. 

In Germany in 1938, Otto Hahn and Fritz Strassmann, skeptical of claims by Enrico Fermi and Irene Johot-Curie that bombardment of uranium by neutrons produced new so-called transuranic elements (elements beyond uranium), repeated these experiments and chemically isolated a radioactive isotope of barium. Unable to interpret these findings, Hahn asked Lise Meitner, a physicist and former colleague, to propose an explanation for his observations. Meitner and her nephew, Otto Frisch, showed that it was possible for the uranium nucleus to be spfit into two smaller nuclei by the neutrons, a process that they termed fission. The discovery of nuclear fission eventually led to the development of nuclear weapons and, after World War II, the advent of nuclear power to generate electricity. Nuclear chemists were involved in the chemical purification of plutonium obtained from uranium targets that had been irradiated in reactors. They also developed chemical separation techniques to isolate radioactive isotopes for industrial and medical uses from the fission products wastes associated with plutonium production for weapons. Today, many of these same chemical separation techniques are being used by nuclear chemists to clean up radioactive wastes resulting from the fifty-year production of nuclear weapons and to treat wastes derived from the production of nuclear power. 

Lanthanum. La at. wt 138,9055 at. no. 57 valence 3. A rare earth metal. Two naturally occurring i 0-ropes 159La <99.911 %) La (0.089%) IJ La is radioactive, 1-12 X 1011 years artificial radioactive isotopes 125-137 140-144. Estimated abundance in earth s crust 5-1 ppm. Found in association with cerium and other light Ian-thanons. Minerals of commercial interest are monazite bastnaesite and cerite. Discovery and isoln Mosander ... 

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... 

Radioactive isotopes for tracer studies may be prepared artificially from nonradioactive elements by bombarding them with suitable nuclear particles produced in a cyclotron or a nuclear reactor. The discovery of this effect was made in 1934 by the French physicists Irene Joliot-Curie (1897-1956) and her husband Frederic Joliot-Curie (1900-1958). They were studying the effect of bombarding light elements such as aluminum with alpha (a) particles, which are beams of helium nuclei, fHe. They noticed that, after the bombardment had ceased, a new form of radiation continued to be emitted, and they concluded that a new isotope had been formed. In the case of the bombardment of ordinary aluminum, HAl, with a particles, the product is an isotopic form of phosphorus, ifP, the most abundant isotope of phosphorus being f P. The process is... 

The presence of radioactivity, both a- and p-particles, in leaf and tobacco smoke has been reported in many publications. At earlier periods, the main concern was for P-activity found in cigars, cigarettes, and tobacco ash (113, 2657, 3367, 20A97). The a-emitting radioactive isotopes were suggested to be significant because of health concerns to smokers. The total a-activity in tobacco varies widely in green leaf, cured leaf tobacco, and tobacco smoke (2466, 3367, 3973). A very minor amount of °Po is transferred into the mainstream smoke (MSS). Twenty-four isotopes have been identified in tobacco smoke. The discovery of elements, isotopes, and ions in tobacco smoke has only been limited by the discovery and advancement of new analytical techniques. 

---