copernicium

Copernicium is a synthetic chemical element with the symbol Cn and atomic number 112. Its known isotopes are extremely radioactive, and have only been created in a laboratory. The most stable known isotope, copernicium-285, has a half-life of approximately 28 seconds. Copernicium was first created in 1996 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It was named after the astronomer Nicolaus Copernicus.

In the periodic table of the elements, copernicium is a d-block transactinide element and a group 12 element. During reactions with gold, it has been shown
to be an extremely volatile element, so much so that it is possibly a gas or a volatile liquid at standard temperature and pressure.

Copernicium is calculated to have several properties that differ from its lighter homologues in group 12, zinc, cadmium and mercury; due to relativistic effects, it may give up its 6d electrons instead of its 7s ones, and it may have more similarities to the noble gases such as radon rather than its group 12 homologues. Calculations indicate that copernicium may show the oxidation state +4, while mercury shows it in only one compound of disputed existence and zinc and cadmium do not show it at all. It has also been predicted to be more difficult to oxidize copernicium from its neutral state than the other group 12 elements. Predictions vary on whether solid copernicium would be a metal, semiconductor, or insulator. Copernicium is one of the heaviest elements whose chemical properties have been experimentally investigated.

Introduction

History

Discovery

Copernicium was first created on February 9, 1996, at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, by Sigurd Hofmann, Victor Ninov et al. This element was created by firing accelerated zinc-70 nuclei at a target made of lead-208 nuclei in a heavy ion accelerator. A single atom of copernicium was produced with a mass number of 277. (A second was originally reported, but was found to have been based on data fabricated by Ninov, and was thus retracted.)

:Pb + Zn → Cn* → Cn + n

In May 2000, the GSI successfully repeated the experiment to synthesize a further atom of copernicium-277.
This reaction was repeated at RIKEN using the Search for a Super-Heavy Element Using a Gas-Filled Recoil Separator set-up in 2004 and 2013 to synthesize three further atoms and confirm the decay data reported by the GSI team.
This reaction had also previously been tried in 1971 at the Joint Institute for Nuclear Research in Dubna, Russia to aim for ²⁷⁶Cn (produced in the 2n channel), but without success.

The IUPAC/IUPAP Joint Working Party (JWP) assessed the claim of copernicium's discovery by the GSI team in 2001 and 2003. In both cases, they found that there was insufficient evidence to support their claim. This was primarily related to the contradicting decay data for the known nuclide rutherfordium-261. However, between 2001 and 2005, the GSI team studied the reaction ²⁴⁸Cm(²⁶Mg,5n)²⁶⁹Hs, and were able to confirm the decay data for hassium-269 and rutherfordium-261. It was found that the existing data on rutherfordium-261 was for an isomer, now designated rutherfordium-261m.

In May 2009, the JWP reported on the claims of discovery of element 112 again and officially recognized the GSI team as the discoverers of element 112. This decision was based on the confirmation of the decay properties of daughter nuclei as well as the confirmatory experiments at RIKEN.

Work had also been done at the Joint Institute for Nuclear Research in Dubna, Russia from 1998 to synthesise the heavier isotope ²⁸³Cn in the hot fusion reaction ²³⁸U(⁴⁸Ca,3n)²⁸³Cn; most observed atoms of ²⁸³Cn decayed by spontaneous fission, although an alpha decay branch to ²⁷⁹Ds was detected. While initial experiments aimed to assign the produced nuclide with its observed long half-life of 3 minutes based on its chemical behaviour, this was found to be not mercury-like as would have been expected (copernicium being under mercury in the periodic table), and indeed now it appears that the long-lived activity might not have been from ²⁸³Cn at all, but its electron capture daughter ²⁸³Rg instead, with a shorter 4-second half-life associated with ²⁸³Cn. (Another possibility is assignment to a metastable isomeric state, ^283mCn.) While later cross-bombardments in the ²⁴²Pu+⁴⁸Ca and ²⁴⁵Cm+⁴⁸Ca reactions succeeded in confirming the properties of ²⁸³Cn and its parents ²⁸⁷Fl and ²⁹¹Lv, and played a major role in the acceptance of the discoveries of flerovium and livermorium (elements 114 and 116) by the JWP in 2011, this work originated subsequent to the GSI's work on ²⁷⁷Cn and priority was assigned to the GSI.

Naming

Using Mendeleev's nomenclature for unnamed and undiscovered elements, copernicium should be known as ''eka- mercury''. In 1979, IUPAC published recommendations according to which the element was to be called ''ununbium'' (with the corresponding symbol of ''Uub''), a systematic element name as a