At the end of the 1930s, a series of experiments showed that bombarding uranium with neutrons produces new radioactive elements, which were assumed to have atomic numbers close to uranium (Z = 92). This assumption arose naturally from the prevailing view of nuclear decay, which involved the emission of only small charged particles (alpha and beta) through explosions. So how could one explain the formation of an element that is almost identical to barium (Z = 56), and thus much smaller than uranium? The answer came in 1939, when Meitner and Frisch proposed a process that involves the addition of one neutron to break apart the uranium nucleus. This process was named “fission,” in analogy to the fission of living cells.
Experiments on Uranium
Experiments conducted by Fermi and his colleagues showed that when uranium was bombarded with neutrons, new radioactive materials were produced, at least four of which were assigned atomic numbers greater than 92. Subsequent investigations revealed at least nine radioactive periods, six of which were assigned to elements that exceed uranium, and it was necessary to assume the existence of a homologous nucleus to explain their chemical behavior alongside their genetic relationships.
Chemical Assumptions
It was always assumed that these radioactive particles had atomic numbers close to the element that was bombarded, since it was only known that singly or doubly charged particles are emitted from the nucleus. For example, it was assumed that the body with properties similar to osmium was eka-osmium (Z = 94) rather than osmium (Z = 76) or ruthenium (Z = 44).
References
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Meitner, L., Hahn, O., and Strassmann, F. (1937). Z. Phys., 106, 249.
Curie, E., and Savitch, P. (1938). C.R., 208, 906, 1643.
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Hahn, O., and Strassmann, F. (1939). Naturwiss., 27, 11.
Bohr, N. (1936). NATURE, 137, 344, 351.
Bohr, N., and Kalkar, F. (1937). Kgl. Danske Vid. Selskab, Math. Phys. Medd., 14, Nr. 10.
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Book Information
The Physics Institute, Academy of Sciences, Stockholm. Source link: https://www.nature.com/nature
Lisa Meitner, Institute of Theoretical Physics, University of Copenhagen. Publication date: January 16. Source link: https://www.nature.com/nature
Ory Frisch, you can also search for this author in PubMed and Google Scholar.
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