Copernicium

Copernicium is a synthetic chemical element; it has 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 30 seconds. Copernicium was first created in February 1996 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It was named after the astronomer Nicolaus Copernicus on his 537th anniversary.<!-- Please do not add nationality here, as this much-debated issue is not relevant to this article. Please refer to the Nicolaus Copernicus article instead -->

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 9 February 1996, at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, by Sigurd Hofmann, Victor Ninov et al.

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. Work had also been done there from 1998 to synthesize 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&nbsp;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), 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. 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&nbsp;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.

Naming

thumb|upright|right|alt=a painted portrait of Copernicus|Element 112 was named to honor [[Nicolaus Copernicus, a scientist from the 16th century a systematic element name as a placeholder, until the element was discovered (and the discovery then confirmed) and a permanent name was decided on. Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations were mostly ignored among scientists in the field, who either called it "element 112", with the symbol of E112, (112), or even simply 112. On 14 July 2009, they proposed copernicium with the element symbol Cp, after Nicolaus Copernicus "to honor an outstanding scientist, who changed our view of the world".

During the standard six-month discussion period among the scientific community about the naming,

it was pointed out that the symbol Cp was previously associated with the name cassiopeium (cassiopium), now known as lutetium (Lu). Moreover, Cp is frequently used today to mean the cyclopentadienyl ligand (C₅H₅). Primarily because cassiopeium (Cp) was (until 1949) accepted by IUPAC as an alternative allowed name for lutetium, the IUPAC disallowed the use of Cp as a future symbol, prompting the GSI team to put forward the symbol Cn as an alternative. On 19 February 2010, the 537th anniversary of Copernicus' birth, IUPAC officially accepted the proposed name and symbol.

Isotopes

Copernicium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Eight different isotopes have been reported with mass numbers 277 and 280–286, and one unconfirmed metastable isomer in ²⁸⁵Cn has been reported. Most of these decay predominantly through alpha decay, but some undergo spontaneous fission, and copernicium-283 may have an electron capture branch.

The isotope copernicium-283 was instrumental in the confirmation of the discoveries of the elements flerovium and livermorium.

Half-lives

All confirmed copernicium isotopes are extremely unstable and radioactive; in general, heavier isotopes are more stable than the lighter, and isotopes with an odd neutron number have relatively longer half-lives due to additional hindrance against spontaneous fission. The most stable known isotope, ²⁸⁵Cn, has a half-life of 30&nbsp;seconds; ²⁸³Cn has a half-life of 4&nbsp;seconds, and the unconfirmed ^285mCn and ²⁸⁶Cn have half-lives of about 15 and 8.45&nbsp;seconds respectively. Other isotopes have half-lives shorter than one&nbsp;second. ²⁸¹Cn and ²⁸⁴Cn both have half-lives on the order of 0.1&nbsp;seconds, and the remaining isotopes have half-lives shorter than one millisecond. These parent nuclei were reported to have successively emitted three alpha particles to form copernicium-281 nuclei, which were claimed to have undergone alpha decay, emitting alpha particles with decay energy 10.68&nbsp;MeV and half-life 0.90&nbsp;ms, but their claim was retracted in 2001 as it had been based on data fabricated by Ninov. This isotope was truly produced in 2010 by the same team; the new data contradicted the previous fabricated data.

The missing isotopes ²⁷⁸Cn and ²⁷⁹Cn are too heavy to be produced by cold fusion and too light to be produced by hot fusion. They might be filled from above by decay of heavier elements produced by hot fusion, and indeed ²⁸⁰Cn and ²⁸¹Cn were produced this way.

Predicted properties

Very few properties of copernicium or its compounds have been measured; this is due to its extremely limited and expensive production and the fact that copernicium (and its parents) decays very quickly. A few singular chemical properties have been measured, as well as the boiling point, but properties of the copernicium metal remain generally unknown and for the most part, only predictions are available.

Chemical

Copernicium is the tenth and last member of the 6d series and is the heaviest group 12 element in the periodic table, below zinc, cadmium and mercury. It is predicted to differ significantly from the lighter group&nbsp;12 elements. The valence s-subshells of the group 12 elements and period 7 elements are expected to be relativistically contracted most strongly at copernicium. This and the closed-shell configuration of copernicium result in it probably being a very noble metal. A standard reduction potential of +2.1&nbsp;V is predicted for the Cn²⁺/Cn couple. Copernicium's predicted first ionization energy of 1155&nbsp;kJ/mol almost matches that of the noble gas xenon at 1170.4&nbsp;kJ/mol. However, it should be able to form metal–metal bonds with copper, palladium, platinum, silver, and gold; these bonds are predicted to be only about 15–20&nbsp;kJ/mol weaker than the analogous bonds with mercury. ab initio calculations at the high level of accuracy predicted that the chemistry of singly-valent copernicium resembles that of mercury rather than that of the noble gases. The latter result can be explained by the huge spin–orbit interaction which significantly lowers the energy of the vacant 7p_1/2 state of copernicium.

Once copernicium is ionized, its chemistry may present several differences from those of zinc, cadmium, and mercury. Due to the stabilization of 7s electronic orbitals and destabilization of 6d ones caused by relativistic effects, Cn²⁺ is likely to have a [Rn]5f¹⁴6d⁸7s² electronic configuration, using the 6d orbitals before the 7s one, unlike its homologues. The fact that the 6d electrons participate more readily in chemical bonding means that once copernicium is ionized, it may behave more like a transition metal than its lighter homologues, especially in the possible +4 oxidation state. In aqueous solutions, copernicium may form the +2 and perhaps +4 oxidation states. In polar solvents, copernicium is predicted to preferentially form the and anions rather than the analogous neutral fluorides (CnF₄ and CnF₂, respectively), although the analogous bromide or iodide ions may be more stable towards hydrolysis in aqueous solution. The anions and should also be able to exist in aqueous solution.

Physical and atomic

Copernicium should be a dense metal, with a density of 14.0&nbsp;g/cm³ in the liquid state at 300&nbsp;K; this is similar to the known density of mercury, which is 13.534&nbsp;g/cm³. (Solid copernicium at the same temperature should have a higher density of 14.7&nbsp;g/cm³.) This results from the effects of copernicium's higher atomic weight being cancelled out by its larger interatomic distances compared to mercury. which would make it the first gaseous metal in the periodic table. with a band gap of around 0.2&nbsp;eV, crystallizing in the hexagonal close-packed crystal structure. 2019 calculations then suggested that in fact copernicium has a large band gap of 6.4 ± 0.2&nbsp;eV, which should be similar to that of the noble gas radon (predicted as 7.1&nbsp;eV) and would make it an insulator; bulk copernicium is predicted by these calculations to be bound mostly by dispersion forces, like the noble gases.

Experimental atomic gas phase chemistry

Interest in copernicium's chemistry was sparked by predictions that it would have the largest relativistic effects in the whole of period&nbsp;7 and group&nbsp;12, and indeed among all 118 known elements. In this experiment, two atoms of copernicium-283 were unambiguously identified and the adsorption properties were interpreted to show that copernicium is a more volatile homologue of mercury, due to formation of a weak metal-metal bond with gold. However, it was pointed out in 2019 that this result may simply be due to strong dispersion interactions. These experiments also allowed the first experimental estimation of copernicium's boiling point: 84&nbsp;°C, so that it may be a gas at standard conditions.

See also

• Island of stability

Notes

References

Bibliography

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External links

• Copernicium at The Periodic Table of Videos (University of Nottingham)