• Controversy on Position Reversal of Four Element Pairs in the Periodic Table

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    • Keywords


      Periodic table, chemical elements, position reversal.

    • Abstract


      In the periodic table of chemical elements, there was a contro-versy on the position of four element pairs—tellurium-iodine, cobalt-nickel, argon-potassium, and thorium-protactinium—where higher atomic weight species were placed just before the lower, i.e., the positions of these pairs of elements were reversed. The proper justification of this position reversal appeared after the publication of Moseley’s work in 1913 when periodicity was redefined as the function of atomic number, not the atomic weight. This controversy surrounding the housing of these four pairs of chemical elements according to their atomic weights, which spanned for more than forty years, and its ultimate solution are briefly delineated in this article.

    • Author Affiliations


      Rajarshi Ghosh1

      1. Department of Chemistry The University of Burdwan Burdwan 713 104, India.
    • Dates


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