Fission, nuclear discovery

In the early years of this century the periodic table ended with element 92 but, with J. Chadwick s discovery of the neutron in 1932 and the realization that neutron-capture by a heavy atom is frequently followed by j6 emission yielding the next higher element, the synthesis of new elements became an exciting possibility. E. Fermi and others were quick to attempt the synthesis of element 93 by neutron bombardment of but it gradually became evident that the main result of the process was not the production of element 93 but nuclear fission, which produces lighter elements. However, in 1940, E. M. McMillan and P. H. Abelson in Berkeley, California, were able to identify, along with the fission products, a short-lived isotope of... 

When the question of the award of a Nobel Prize in Physics for the discovery of nuclear fission arose at the end of World War II, it was complicated by the fact that both Hahn and Strassmann were chemists. Another complication was that the Nobel Prize Committee had always considered radioactivity and radioactive atoms the responsibility of their chem-istiy committee—despite the fact that the discovery of fission had been interdisciplinai y from beginning to end. The Swedish Academy of Science was divided on whether the Chemistry Prize should be given jointly to Hahn and Meitner, or to Hahn alone. Finally they decided by a close vote to give the 1945 chemistry prize solely to Otto Hahn. 

Nuclear fission is a process in which a heavy nucleus—usually one with a nucleon number of two hundred or more—separates into two nuclei. Usually the division liberates neutrons and electromagnetic radiation and releases a substantial amount of energy. The discoveiyi of nuclear fission is credited to Otto I lahn and Fritz Strassman. In the process of bombarding uranium with neutrons in the late 1930s, they detected several nuclear products of significantly smaller mass than uranium, one of which was identified as Ba. The theorectical underpinnings that exist to this day for nuclear fission were proposed by Lise Meitner and Otto Frisch. Shortly after Hahn and Strassman s discovery. 

Frederick Soddy (1921, chemistry description of isotopes) Otto Hahn (1944, chemistry discovery of nuclear fission)... 

The development of chemistry itself has progressed significantly by analytical findings over several centuries. Fundamental knowledge of general chemistry is based on analytical studies, the laws of simple and multiple proportions as well as the law of mass action. Most of the chemical elements have been discovered by the application of analytical chemistry, at first by means of chemical methods, but in the last 150 years mainly by physical methods. Especially spectacular were the spectroscopic discoveries of rubidium and caesium by Bunsen and Kirchhoff, indium by Reich and Richter, helium by Janssen, Lockyer, and Frankland, and rhenium by Noddack and Tacke. Also, nuclear fission became evident as Hahn and Strassmann carefully analyzed the products of neutron-bombarded uranium. 

H. Bethe and C. von Weizsacker discover CNO cycle and pp chain. Discovery of nuclear fission (Hahn, Strassmann, Meitner, Frisch). 

Stopping power has been the subject of study for more than a century beginning with the pioneering work of Thompson and Rutherford. With the discovery of nuclear fission... 

HANN, OTTO (1879-1968). A German physical chemist who won the Nobel prize for chemistry in 1944 for his discovery of Ihe fission of heavy nuclei and the principle of the chain reaction, Well-known lor work on nuclear fission he discovered prnlactinium and iransuranium elements with atomic numbers 94. 95, and 96. After receiving his doctorate at the University of Munich, he worked in Canada before returning to Europe. 

The first scientific attempts to prepare the elements beyond uranium were performed by Enrico Fermi, Emilio Segre, and co-workers in Rome in 1934, shortly after the existence of the neutron was discovered. This group of investigators irradiated uranium with slow neutrons and found several radioactive products, which were thought to be due to new elements. However, detailed chemical studies by Otto Hahn and Fritz Strassman in Berlin showed these species were isotopes of the known elements created by the fission of uranium into two approximately equal parts (see Chap. 11). This discovery of nuclear fission in December of 1938 was thus a by-product of man s quest for the transuranium elements. 

The discovery in 1938-1939 of nuclear fission of uranium, which led ultimately to the discovery of nuclear power, heralded a new, extraordinarily fruitful stage in Ya.B. s scientific activity. His interests were concentrated on the study of the mechanism of fission of heavy nuclei and, what proved particularly important, on the development of a theory of the chain fission reaction of uranium. During 1939-1943 Ya.B. wrote several papers which laid the foundation for this subject and were of fundamental value. We note that four of these papers, written in collaboration with Yu. B. Khariton, were done practically in two years before the war. The papers of this series form the foundation of modern physics of reactors and nuclear power they are widely known and do not require special commentary—a short review of the basic physical results is eloquent enough. 

Ida Noddack s proposal of the fission process has awakened interest in the history of science since Gerald Holton unearthed the case in 1973. See T. Hopper, She was ignored. Ida Noddack and the Discovery of Nuclear Fission, Master s thesis, Stanford University, 1990, and F. Habashi, Ida Noddack proposes of nuclear fission, in M.F, Rayner-Canham and G.W. Rayner-Canham (eds.), A Devotion to their Science Pioneer Women in Radioactivity (Philadelphia Chemical Heritage Foundation - Me Gill s University Press, 1997), 217-225. 

The Search for Artificial Elements and the Discovery of Nuclear Fission... 

With this, the goals of those who first sought artificial elements beyond uranium were realized. The understanding of nuclear behavior was deepened by the discovery of nuclear fission, and the periodic system was extended and clarified by the synthesis of transuranium elements. 

Hiroshima exploded with energy equivalent to about 20,000 tons of TNT.18 But where does all of this energy come from Unlike ordinary chemical reactions, nuclear fission does not involve breaking and forming chemical bonds. Instead, the energy comes from the loss of mass that accompanies the fission reaction. Most, if not all, of the students will be familiar with Einstein s famous equation, E = me2, but few are likely to understand what it means.19 In 1939, Lise Meitner and her nephew Robert Frisch reported their discovery of nuclear fission.20 They realized that the energy that accompanied the fission of uranium nuclei could be accounted for by using Einstein s equation. 

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