Lo! There *IS* something new under the Sun! / copernicium = Element 112 named for Copernicus / It's Hot Stuff!

Post to "Basement & Garage Ionizing Radiation Afficionadi":

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This is hot off the press and down and dirty.

The IUPAC announcement is perfectly trustworthy, but contains few of the physics and chemistry details.

This isn't the moment of discovery of element 112, but rather the occasion of settling a dispute over who gets credit for discovering it, and naming it -- the credited discoverers get the privilege of naming it.

The Wikipedia wiki has physics and chemistry details ... but its trustworthiness is largely a function of the wiki author. But for now, this is the best and quickest skinny there is.

IT IS PURELY A COINCIDENCE THAT I'M POSTING ON APRIL FOOL'S DAY. (The IUPAC notice is 29 March.)

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IUPAC
International Union of Pure and Applied Chemistry

Last update: 29 March 2010

Element 112 is Named Copernicium

IUPAC has officially approved the name copernicium, with symbol Cn, for the element of atomic number 112. Priority for the discovery of this element was assigned, in accordance with the agreed criteria, to the Gesellschaft für Schwerionenforschung (GSI) (Center for Heavy Ion Research) in Darmstadt, Germany. The team at GSI proposed the name copernicium which has now been approved by IUPAC. Sigurd Hofmann, leader of the GSI team stated that the intent was to "salute an influential scientist who didn't receive any accolades in his own lifetime, and highlight the link between astronomy and the field of nuclear chemistry."

The name proposed by the Gesellschaft für Schwerionenforschung (GSI) lies within the long tradition of naming elements to honor famous scientists. Nicolaus Copernicus was born on 19 February 1473, in Torún, Poland and died on 24 May 1543, in Frombork/Frauenburg also in Poland. His work has been of exceptional influence on the philosophical and political thinking of mankind and on the rise of modern science based on experimental results. During his time as a canon of the Cathedral in Frauenburg, Copernicus spent many years developing a conclusive model for complex astronomical observations of the movements of the sun, moon, planets and stars. His work published as “De revolutionibus orbium coelestium, liber sixtus” in 1543 had very far reaching consequences. Indeed the Copernican model demanded major changes in the view of the world related to astronomy and physical forces and well as having theological and political consequences. The planetary system introduced by Copernicus has been applied to other analogous systems in which objects move under the influence of a force directed towards a common centre. Notably, on a microscopic scale this is the Bohr model of the atom with its nucleus and orbiting electrons.

The Recommendations will be published in the March issue of the IUPAC journal Pure and Applied Chemistry and is available online at Pure Appl. Chem., 2010, Vol. 82, No. 3, pp. pp 753-755 (doi: 10.1351/PAC-REC-09-08-20). Priority of claims to the discovery of the element of atomic number 112 was determined by a joint working party of independent experts drawn from the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP). The group’s report was published in July 2009, Pure Appl. Chem., 2009, Vol. 81, No. 7, pp. 1331-1343 (doi: 10.1351/PAC-REP-08-03-05). The Joint Working Party will issue a second report, dealing with claims for the discovery of elements with atomic numbers in the range 113 to 118, in the near future.

IUPAC was formed in 1919 by chemists from industry and academia. For more than 90 years, the Union has succeeded in fostering worldwide communications in the chemical sciences and in uniting academic, industrial and public sector chemistry in a common language. IUPAC is recognized as the world authority on chemical nomenclature, terminology, standardized methods for measurement, atomic weights and many other critically evaluated data. More information about IUPAC and its activities is available at www.iupac.org.

For questions, contact Dr. Terrence Renner, Executive Director, at .

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Wikipedia
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Copernicium is a synthetic radioactive chemical element with the symbol Cn and atomic number 112. The element was previously known by the IUPAC systematic element name ununbium (pronounced /uːnˈuːnbiəm/ ( listen)[1] oon-OON-bee-əm), with the symbol Uub. It was first created in 1996 by the Gesellschaft für Schwerionenforschung (GSI).

Copernicium is currently the highest-numbered element to be officially recognised by the International Union of Pure and Applied Chemistry (IUPAC). The most stable isotope discovered to date is 285Cn with a half-life of ≈30 s, although evidence exists that 285Cn may have a nuclear isomer with a much longer half-life of 8.9 min. In total, about 75 atoms of copernicium have been detected using various nuclear reactions.[2] Recent experiments suggest that copernicium behaves as a typical member of group 12, demonstrating properties consistent with a volatile metal.[3]

History
Official 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.[4] 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 (the second has subsequently been dismissed) of copernicium was produced with a mass number of 277.[4]

20882Pb + 7030Zn → 278112Cn → 277112Cn + 10n

In May 2000, the GSI successfully repeated the experiment to synthesise a further atom of Cn-277.[5][6] This reaction was repeated at RIKEN using the GARIS set-up in 2004 to synthesise two further atoms and confirm the decay data reported by the GSI team.[7]

The IUPAC/IUPAP Joint Working Party (JWP) assessed the claim of discovery by the GSI team in 2001[8] and 2003.[9] 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 isotope 261Rf. However, between 2001 and 2005, the GSI team studied the reaction 248Cm(26Mg,5n)269Hs, and were able to confirm the decay data for 269Hs and 261Rf. It was found that the existing data on 261Rf was for an isomer,[10] now designated 261a Rf.

In May 2009, the JWP reported on the claims of discovery of element 112 again and officially recognised the GSI team as the discoverers of element 112.[11] This decision was based on recent confirmation of the decay properties of daughter nuclei as well as the confirmatory experiments at RIKEN.[12]

Naming

After acknowledging their discovery, the IUPAC asked the discovery team at GSI to suggest a permanent name for ununbium.[13][14] 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."[15] IUPAC delayed the official recognition of the name, pending the results of a six-month discussion period among the scientific community.[16][17]

Alternative spellings had been suggested to Hofmann, namely "copernicum", "copernium", and "kopernikium" (Kp), and Hofmann has said that the team had discussed the possibility of "copernicum" or "kopernikum", but that they had agreed on "copernicium" in order to comply with current IUPAC rules, which allow only the suffix -ium for new elements.[18][citation needed]

However, it was pointed out that the symbol Cp was previously associated with the name cassiopeium (cassiopium), now known as lutetium (Lu).[19][20] Furthermore, the symbol Cp is also used in organometallic chemistry to denote the ligand cyclopentadiene. For this reason, 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 February 19, 2010, the 537th anniversary of Copernicus' birth, IUPAC officially accepted the proposed name and symbol.[21][22]

Isotopes and nuclear properties
Nucleosynthesis

Target-projectile combinations leading to Z=112 compound nuclei
The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=112.

Target Projectile CN Attempt result
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208Pb 70Zn 278Cn Successful reaction
232Th 50Ti 282Cn Reaction yet to be attempted
238U 48Ca 286Cn Successful reaction
244Pu 40Ar 284Cn Reaction yet to be attempted
248Cm 36S 284Cn Reaction yet to be attempted
249Cf 30Si 279Cn Reaction yet to be attempted
================================================

Cold fusion

This section deals with the synthesis of nuclei of copernicium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.

208Pb(70Zn,xn)278-xCn (x=1)

The team at GSI first studied this reaction in 1996 and reported the detection of two decay chains of 277Cn.[4] In a review of the data in 2000, the first decay chain was retracted. In a repeat of the reaction in 2000 they were able to synthesise a further atom. They attempted to measure the 1n excitation function in 2002 but suffered from a failure of the Zn-70 beam. The unofficial discovery of 277Cn was confirmed in 2004 at RIKEN, where researchers detected a further two atoms of the isotope and were able to confirm the decay data for the entire chain.

208Pb(68Zn,xn)276-xCn

After the successful synthesis of 277Cn, the GSI team performed a reaction using a 68Zn projectile in 1997 in an effort to study the effect of isospin (neutron richness) on the chemical yield. The experiment was initiated after the discovery of a yield enhancement during the synthesis of darmstadtium isotopes using 62Ni and 64Ni ions. No decay chains of 275Cn were detected leading to a cross section limit of 1.2 pb. However, the revision of the yield for the 70Zn reaction to 0.5 pb does not rule out a similar yield for this reaction.

184W(88Sr,xn)272-xCn

In 1990, after some early indications for the formation of isotopes of element 112 in the irradiation of a tungsten target with multi-GeV protons, a collaboration between GSI and the University of Jerusalem studied the foregoing reaction. They were able to detect some spontaneous fission activity and a 12.5 MeV alpha decay, both of which they tentatively assigned to the radiative capture product 272Cn or the 1n evaporation residue 271Cn. Both the TWG and JWP have concluded that a lot more research is required to confirm these conclusions.

Hot fusion

This section deals with the synthesis of nuclei of copernicium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40–50 MeV, hence "hot"), leading to a reduced probability of survival from fission and quasi-fission. The excited nucleus then decays to the ground state via the emission of 3–5 neutrons. Fusion reactions utilizing 48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30–35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.
238U(48Ca,xn)286-xCn (x=3,4)

In 1998, the team at the Flerov Laboratory of Nuclear Research began a research program using Ca-48 nuclei in "warm" fusion reactions leading to superheavy elements (SHE's). In March 1998, they claimed to have synthesised the element (two atoms) in this reaction. The product, 283Cn, had a claimed half-life of 5 min, decaying by spontaneous fission (SF).[23]

The long lifetime of the product initiated first chemical experiments on the gas phase atomic chemistry of element 112. In 2000, Yuri Yukashev at Dubna repeated the experiment but was unable to observe any spontaneous fission from 5 min activities. The experiment was repeated in 2001 and an accumulation of eight fragments resulting from spontaneous fission were found in the low-temperature section, indicating that copernicium had radon-like properties. However, there is now some serious doubt about the origin of these results.

In order to confirm the synthesis, the reaction was successfully repeated by the same team in Jan 2003, confirming the decay mode and half life. They were also able to calculate an estimate of the mass of the spontaneous fission activity to ~285 lending support to the assignment.[24]

The team at LBNL entered the debate and performed the reaction in 2002. They were unable to detect any spontaneous fission and calculated a cross section limit of 1.6 pb for the detection of a single event.[25]

The reaction was repeated in 2003–2004 by the team at Dubna using a slightly different set-up, the Dubna Gas Filled Recoil Separator (DGFRS). This time, 283Cn was found to decay by emission of a 9.53 MeV alpha-particle with a half-life of 4 seconds. 282Cn was also observed in the 4n channel.[26]

In 2003, the team at GSI entered the debate and performed a search for the five-minute SF activity in chemical experiments. Like the Dubna team, they were able to detect seven SF fragments in the low temperature section. However, these SF events were uncorrelated, suggesting they were not from actual direct SF of copernicium nuclei and raised doubts about the original indications for radon-like properties.[27] After the announcement from Dubna of different decay properties for 283Cn, the GSI team repeated the experiment in September 2004. They were unable to detect any SF events and calculated a cross section limit of ~ 1.6 pb for the detection of one event, not in contradiction with the reported 2.5 pb yield by Dubna.

In May 2005, the GSI performed a physical experiment and identified a single atom of 283Cn decaying by SF with a short lifetime suggesting a previously unknown SF branch.[28] However, initial work by Dubna had detected several direct SF events but had assumed that the parent alpha decay had been missed. These results indicated that this was not the case.

In 2006, the new decay data on 283Cn was confirmed by a joint PSI-FLNR experiment aimed at probing the chemical properties of copernicium. Two atoms of 283Cn were observed in the decay of the parent 287Uuq nuclei. The experiment indicated that contrary to previous experiments, copernicium behaves as a typical member of group 12, demonstrating properties of a volatile metal.[3]

Finally, the team at GSI successfully repeated their physical experiment in Jan 2007 and detected three atoms of 283Cn, confirming both the alpha and SF decay modes.[29]

As such, the 5 min SF activity is still unconfirmed and unidentified. It is possible that it refers to an isomer, namely 283bCn, whose yield is dependent upon the exact production methods.

233U(48Ca,xn)281-xCn

The team at FLNR studied this reaction in 2004. They were unable to detect any atoms of element 112 and calculated a cross section limit of 600 fb. The team concluded that this indicated that the neutron mass number for the compound nucleus had an effect on the yield of evaporation residues.[26]

As a decay product

Copernicium has also been observed as decay products of elements 114, 116, and 118 (see ununoctium).

Evaporation Residue Observed Cn isotope
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293Uuh, 289Uuq 285Cn
292Uuh, 288Uuq 284Cn
291Uuh, 287Uuq 283Cn
294Uuo, 290Uuh, 286Uuq 282Cn
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As an example, in May 2006, the Dubna team (JINR) identified 282Cn as a final product in the decay of ununoctium via the alpha decay sequence.

294118Uuo → 290116Uuh → 286114Uuq → 282112Cn

It was found that the final nucleus undergoes spontaneous fission.[30]

Retracted isotopes
281Cn

In the claimed synthesis of 293Uuo in 1999 (see ununoctium) the isotope 281Cn was identified as decaying by emission of a 10.68 MeV alpha particle with half-life 0.90 ms. The claim was retracted in 2001 and hence this copernicium isotope is currently unknown or unconfirmed.

Chronology of isotope discovery

Isotope Year discovered discovery reaction
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277Cn 1996 208Pb(70Zn,n)
278Cn unknown
279Cn unknown
280Cn unknown
281Cn unknown
282Cn 2004 238U(48Ca,4n)
283Cn 2002 244Pu(48Ca,5n)
283bCn ?? 1998 238U(48Ca,3n)
284Cn 2002 244Pu(48Ca,4n)
285Cn 1999 244Pu(48Ca,3n)
285bCn ? 1999 244Pu(48Ca,3n)
============================================

Nuclear isomerism
285a,bCn

In the synthesis of 289Uuq and 293Uuh, a 8.63 MeV alpha-decaying activity has been detected with a half-life of 8.9 minutes. Although unconfirmed in recent experiments, it is highly possible that this is associated with an isomer, namely 285bCn.

283a,bCn

First experiments on the synthesis of 283Cn produced a SF activity with half-life ~5 min. This activity was also observed from the alpha decay of 287Uuq. The decay mode and half-life were also confirmed in a repetition of the first experiment. However, more recently,283Cn has been observed to undergo 9.52 MeV alpha decay and SF with a half-life of 3.9 s. These results suggest the assignment of the two activities to two different isomeric levels in 283Cn, creating 283aCn and 283bCn. Further research is required to address these discrepancies.

Chemical yields of isotopes
Cold fusion

The table below provides cross-sections and excitation energies for cold fusion reactions producing copernicium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile Target CN 1n 2n 3n
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70Zn 208Pb 278Cn 0.5 pb, 10.0, 12.0 MeV
68Zn 208Pb 276Cn <1.2>
===========================================

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing copernicium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile Target CN 3n 4n 5n
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48Ca 238U 286Cn 2.5 pb, 35.0 MeV 0.6 pb
48Ca 233U 281Cn <0.6 pb, 34.9 MeV ===========================================

Fission of compound nuclei with Z=112

Several experiments have been performed between 2001 and 2004 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus 286Cn. The nuclear reaction used is 238U+48Ca. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as 132Sn (Z=50, N=82). It was also found that the yield for the fusion-fission pathway was similar between 48Ca and 58Fe projectiles, indicating a possible future use of 58Fe projectiles in superheavy element formation.[31]

Theoretical calculations
Evaporation residue cross sections

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

DNS = Di-nuclear system; σ = cross section

Target Projectile CN Channel (product) σmax Model Ref
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208Pb 70Zn 278Cn 1n (277Cn) 1.5 pb DNS [32]
208Pb 67Zn 275Cn 1n (274Cn) 2 pb DNS [32]
238U 48Ca 286Cn 4n (282Cn) 0.2 pb DNS [33]
244Pu 40Ar 284Cn 4n (280Cn) 0.1 pb DNS [33]
250Cm 36S 286Cn 4n (282cn) 5 pb DNS [33]
252Cf 30Si 282Cn 3n (279Cn) 10 pb DNS [33]
==========================================================

Chemical properties
Extrapolated chemical properties
Oxidation states

Copernicium is the last member of the 6d series of transition metals and the heaviest member of group 12 (IIB) in the Periodic Table, below zinc, cadmium and mercury. Each of the members of this group show a stable +2 oxidation state. In addition, mercury(I), Hg2+2, is also well known. Copernicium is therefore expected to form a stable +2 state.

Chemistry

The known members of group 12 all react with oxygen and sulfur directly to form the oxides and sulfides, MO and MS, respectively. Mercury(II) oxide, HgO, can be decomposed by heat to the liquid metal. Mercury also has a well known affinity for sulfur. Therefore, copernicium should form an analogous oxide CnO and sulfide CnS.

In their halogen chemistry, all the metals form the ionic difluoride MF2 upon reaction with fluorine. The other halides are known but for mercury, the soft nature of the Hg(II) ion leads to a high degree of covalency and HgCl2, HgBr2 and HgI2 are low-melting, volatile solids. Therefore, copernicium is expected to form an ionic fluoride, CnF2, but volatile halides, CnCl2, CnBr2 and CnI2.

In addition, mercury is well known for its alloying properties, with the concomitant formation of amalgams, especially with gold and silver. It is also a volatile metal and is monatomic in the vapour phase. Copernicium is therefore also predicted to be a volatile metal which readily combines with gold to form a Au-Cn metal-metal bond.

[more at Copernicium wiki]