Roentgenium

Roentgenium (pronEng|rɛntˈgɛniəm, IPA|/rʌntˈdʒɛniəm/ [ [http://dictionary.reference.com/browse/Roentgenium Roentgenium - Definitions from Dictionary.com ] ] ) is a chemical element in the periodic table that has the symbol Rg and atomic number 111.It is a synthetic element whose most stable known isotope has a mass of 283 and an estimated half-life of ten minutes.

Official discovery

Element 111 was officially discovered by Peter Armbruster, Gottfried Münzenber, and their team working at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany on December 8, 1994. [http://springerlink.com/content/k27n1510t165q17n "The new element 111"] , Hofmann et al., Z. Phys. A., 1995, 350, 4. Retrieved on 2008-03-02/] Only three atoms of it were observed (all ²⁷²Rg), by the cold fusion between ⁶⁴Ni ions and a ²⁰⁹Bi target in a linear accelerator:

:su|p=209|b=83|a=rBi + su|p=64|b=28Ni → su|p=272|b=111Rg + su|p=1|b=0n

In 2001, the IUPAC/IUPAP Joint Working Party (JWP) from concluded that there was insufficient evidence for the discovery at that moment in time. [ [http://iupac.org/publications/pac/2001/pdf/7306x0959.pdf "ON THE DISCOVERY OF THE ELEMENTS 110–112"] , Karol et al., "Pure Appl. Chem.", Vol. 73, No. 6, pp. 959–967, 2001. Retrieved on 2008-03-02] The GSI team repeated their experiment in 2000 and detected a further 3 atoms. [http://springerlink.com/content/b8hxq636ubkc47j2 "New results on elements 111 and 112"] , Hofmann et al., "Eur. Phys. J. A.", 2002, 14, 2. Retrieved on 2008-03-02/] [ [http://www.gsi.de/informationen/wti/library/scientificreport2000/Nuc_St/7/ar-2000-z111-z112.pdf "New results on element 111 and 112"] , Hofmann et al., "GSI report 2000". Retrieved on 2008-03-02] In their 2003 report, the JWP decided that the GSI team should be acknowledged as the discoverers. [ [http://iupac.org/publications/pac/2003/pdf/7510x1601.pdf "ON THE CLAIMS FOR DISCOVERY OF ELEMENTS 110, 111, 112, 114, 116, AND 118*"] , Karol et al., "Pure Appl. Chem.", Vol. 75, No. 10, pp. 1601–1611, 2003. Retrieved on 2008-03-02]

Proposed name

The name "roentgenium" (Rg) was proposed by the GSI team [ [http://iupac.org/reports/provisional/abstract04/Corish_pr111.pdf "NAME AND SYMBOL OF THE ELEMENT WITH ATOMIC NUMBER 111"] , Corish et al., "IUPAC Provisional Recommendations". Retrieved on 2008-03-02] and was accepted as a permanent name on November 1 2004 in honor of the German physicist Wilhelm Conrad Röntgen. [ [http://iupac.org/publications/pac/2004/pdf/7612x2101.pdf "Name and symbol of the element with atomic number 111"] , Corish et al., "Pure Appl. Chem.", 2004, Vol. 76, No. 12, pp. 2101-2103. Retrieved on 2008-03-02] Previously the element was known under the temporary IUPAC systematic element name "unununium" (pronEng|ˌjuːnənˈjuːniəm or IPA|/ˌʌnəˈnʌniəm/ [ [http://dictionary.reference.com/unununium] ] ), "Uuu". Some research has referred to it as "eka-gold".

Electronic structure

Non-relativistic

Roentgenium has 6 full shells, 7s+5p+3d+2f=17 full subshells, and 111 orbitals:

Bohr model: 2, 8, 18, 32, 32, 18, 1

Quantum mechanical model: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s¹5f¹⁴6d¹⁰

Relativistic

The stable group 11 elements, copper, silver, and gold all have an outer electron configuration nd¹⁰(n+1)s¹. For each of these elements, their first excited state has a configuration nd⁹(n+1)s². Due to spin-orbit coupling between the s electrons, this state is split into a pair of energy levels. For copper, the difference in energy between the ground state and lowest excited state causes the metal to appear reddish. For silver, the energy gap widens and it become silvery. However, as Z increases, the excited levels are stabilised by relativistic effects and in gold the energy gap decreases again and it appears gold. For roentgenium, calculations indicate that the 6d⁹7s² level is stabilised to such an extent that it becomes the ground state. The resulting energy difference between the new ground state and the first excited state is similar to that of silver and roentgenium is expected to be silvery in appearance. [ [http://wwwsoc.nii.ac.jp/jnrs/paper/JN52/j052Turler.pdf "Gas Phase Chemistry of Superheavy Elements"] , Turler, A., "Journal of Nuclear and Radiochemical Sciences", Vol. 5, No.2, pp. R19-R25, 2004. Retrieved on 2008-03-03]

Extrapolated chemical properties of eka-gold

Oxidation states

Element 111 is projected to be the ninth member of the 6d series of transition metals and the heaviest member of group 11 (IB) in the Periodic Table, below copper, silver, and gold. Each of the members of this group show different stable states. Copper forms a stable +II state, whilst silver is predominantly found as Ag(I) and gold as Au(III). Copper(I) and silver(II) are also relatively well-known. Roentgenium is therefore expected to predominantly form a stable +III state.

Chemistry

The heavier members of this group are well known for their lack of reactivity or noble character. Silver and gold are both inert to oxygen. They are both however attacked by the halogens. In addition, silver is attacked by sulfur and hydrogen sulfide, highlighting its higher reactivity compared to gold. Roentgenium is expected to be even more noble than gold and can be expected to be inert to oxygen and halogens. The most-likely reaction is with fluorine to form a trifluoride, RgF₃.

History of synthesis of isotopes by cold fusion

=²⁰⁹Bi(⁶⁴Ni,xn)^273−xRg (x=1)=

First experiments to synthesize element 111 were performed by the Dubna team in 1986 using this cold fusion reaction. No atoms were identified that could be assigned to atoms of element 111 and a production cross-section limit of 4 pb was determined. After an upgrade of their facilities, the team at GSI successfully detected 3 atoms of ²⁷²Rg in their discovery experiment. A further 3 atoms were synthesized in 2000. The discovery of roentgenium was confirmed in 2003 when a team at RIKEN measured the decays of 14 atoms of ²⁷²Rg during the measurement of the 1n excitation function. [ [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVB-4GST10Y-N&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ed38b3cbabf32e057b4328ad84e5d886 "Status of heavy element research using GARIS at RIKEN"] , Morita et al., "Nucl. Phys. A734", 101 (2004). Retrieved on 2008-03-03]

=²⁰⁸Pb(⁶⁵Cu,xn)^273−xRg (x=1)=

In 2004, as part of their study of odd-Z projectiles in cold fusion reactions, the team at LBNL detected a single atom of ²⁷²Rg in this new reaction. [ [http://prola.aps.org/abstract/PRL/v93/i21/e212702 "Development of an Odd-Z-Projectile Reaction for Heavy Element Synthesis: ²⁰⁸Pb(⁶⁴Ni,n)²⁷¹Ds and ²⁰⁸Pb(⁶⁵Cu,n)²⁷²111"] , Folden et al., "Phys. Rev. Lett.", 93, 212702 (2004). Retrieved on 2008-03-02] [ [http://repositories.cdlib.org/cgi/viewcontent.cgi?article=2704&context=lbnl "Development of an Odd-Z-Projectile Reaction for Heavy Element Synthesis: ²⁰⁸Pb(⁶⁴Ni,n)²⁷¹Ds and ²⁰⁸Pb(⁶⁵Cu,n)²⁷²111"] , Folden et al., "LBNL repositories". Retrieved on 2008-03-02]

History of synthesis of isotopes as decay products

Isotopes of roentgenium have also been observed in the decay of heavier elements. Observations to date are outlined in the table below:

Isotopes

Five isotopes of roentgenium are known. The longest-lived of these is ²⁸⁰Rg, which decays through alpha decay and has a halflife of 3.6 seconds. The shortest-lived isotope is ²⁷²Rg, which decays through alpha decay and has a halflife of 1.6 ms.

Isomerism in roentgenium nuclides

²⁷⁴Rg

Two atoms of ²⁷⁴Rg have been observed in the decay chains starting with ²⁷⁸Uut. The two events occur with different energies and with different lifetimes. In addition, the two entire decay chains appear to be different. This suggests the presence of two isomeric levels but further research is required.

²⁷²Rg

The direct production of ²⁷²Rg has provided four alpha lines at 11.37, 11.03, 10.82, and 10.40 MeV. The GSI measured a half-life of 1.6 ms whilst recent data from RIKEN has given a half-life of 3.8 ms. The conflicting data may be due to isomeric levels but the current data are insufficient to come to any firm assignments.

Future experiments

To date there has been no attempt to synthesise roentgenium in hot fusion reactions. It has been mentioned by the Dubna team that they could complete their Ca-48 projectile program by studying the reaction

:su|p=231|b=91|a=rPa + su|p=48|b=20Ca → su|p=279|b=111Rg → su|p=276, 275, 274|b=111|a=rRg

References

ee also

*Island of stability

External links

* [http://webelements.com/webelements/elements/text/Rg/index.html WebElements.com: Roentgenium]
* [http://iupac.org/reports/provisional/abstract04/corish_311004.html IUPAC: Proposal of name "roentgenium" for element 111]
* [http://iupac.org/news/archives/2004/naming111.html IUPAC: Element 111 is named roentgenium]
* [http://www.apsidium.com/elements/111.htm Apsidium: Roentgenium 111]
* [http://www.chemicalelements.com/elements/uuu.html Unununium Element At Chemicalelements.com]