On 27 August 2013 it was announced that scientists from Lund in Sweden had obtained good evidence for the existence of element 115. This event inevitably sets up speculation as to what the element may eventually be named and what its symbol might be. Of course these matters will be adjudicated by the appropriate IUPAC committee and the outcomes will be rapidly disseminated around the world.
In this short communication, I would like to sound a warning about the choice of symbol, in particular, and to mention something that happened over the choice of symbol for element 112, which was named copernicium.
After this element was initially discovered and subsequently approved, the discoverers at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, proposed the symbol Cp. But during the obligatory six-month period of discussion that followed this proposal it was pointed out that Cp had once been used for an element “cassiopeium” which subsequently became known as lutetium. As in the case of any name proposed for an element that is subsequently rejected, any symbol for a rejected element can also never be used again. As a result IUPAC asked the discoverers to choose another symbol, whereupon Cn was proposed and duly ratified.
There is just one further problem. Although nobody seems to have noticed at the time, the symbol Cn had also once been proposed for an element, coronium, whose name and symbol were published in several articles by the English physicist and mathematician John Nicholson almost exactly 100 years ago. In an ingenious theory that involved the postulation of several proto-elements, Nicholson rather successfully explained numerous unidentified spectral lines in gaseous nebulae as well as the solar corona. Moreover Nicholson successfully predicted several spectral lines in these two kinds of astronomical bodies. His theory was quickly eclipsed by Bohr’s theory of the hydrogen atom and very little of Nicholson was heard of subsequently. It is rather remarkable that he should have achieved the success that he did given that none of his proto-elements such as nebulium or coronium actually exist.
Element names such as mosleyum, which might have made an excellent choice in this the year of the centenary of Moseley’s great discovery, have been ruled out on the basis that they referred to elements that were once proposed and then rejected. So let’s try to make sure that whatever name and symbol are chosen for element 115 are indeed unique and have never previously been published.