User talk:68.60.68.203/transuranium/
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The first attempt to produce a transuranium element was made in 1934 in Rome, where a team of Italian physicists headed by Enrico Fermi and Emilio Segrè bombarded uranium nuclei with free neutrons.[1]
They chose to bombard the heavy radioactive elements thorium and uranium, as the general instability of nuclei in this range of atomic weight might give rise to successive transformations Fermi proposed that radioactivity resulting from bombardment of uranium by neutrons, might be evidence for the production of element Z=93.
Ida Noddack found fault with the methodology of his proof.
Fermi compared his new beta emitter not only with the immediate neighbor of uranium, namely protactinium, but also considered several other elements down to lead. This indicates that he thought a series of consecutive decays was possible...It is not clear why he did not investigate the element polonium (84) which is also between uranium (92) and lead (82), and why he chose to stop at lead.The old view that the radioactive elements form a continuous series which ends at lead or thallium (81) is just what the previously mentioned experiments of Curie and Joliot had disproved. Fermi therefore ought to have compared his new radioelement with all known elements...the proof that the new (13 minute) radioelement has atomic number 93 is in no sense successful, since Fermi's method of eliminating other possibilities has not been carried through to completion.
What was only later considered especially noteworthy in Noddack's paper was her suggestion that: One could assume equally well that when neutrons are used to produce nuclear disintegrations, some distinctly new nuclear reactions take place which have not been observed previously with proton or alpha-particle bombardment of atomic nuclei. In the past one has found that transmutations of nuclei only take place with the emission of electrons, protons, or helium nuclei, so that the heavy elements change their mass only a small amount to produce near neighboring elements. When heavy nuclei are bombarded by neutrons, it is conceivable that the nucleus breaks up into several large fragments, which would of course be isotopes of known elements but would not be neighbors of the irradiated element.
However there was at the time no theoretical basis for this suggestion, and Noddack offered none. [2]
The first transuranium elements were soon discovered as a result of the effort to produce an atomic bomb in the U.S.
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- ^ In this way it appears that we have excluded the possibility that the 13 min-activity is due to isotopes of uranium (92), protactinum (91), thorium (90), actinium (89), radium (88), bismuth (83), lead (82). Its behavior excludes also ekacaesium (87) and emanation (86). This negative evidence about the identity of the 13 min-activity from a large number of heavy elements suggests the possibility that the atomic number of the element may be greater than 92. If it were an element 93, it would be chemically homologous with manganese and rhenium. This hypothesis is supported to some extent also by the observed fact that the 13 min-activity is carried down by a precipitate of rhenium. sulphide insoluble in hydrochloric acid. However, as several elements are easily precipitated in this form, this evidence cannot be considered as very strong. FERMI, E. (1934). "Possible Production of Elements of Atomic Number Higher than 92". Nature 133: p. 898-899.
- ^ NODDACK, IDA (September, 1934). "On Element 93" (English Translation). Zeitschrift fur Angewandte Chemie 47: p. 653.
- ^ zz"" .
