Ununoctium (IPA pronunciation: /ˌjuːnəˈnɒktiəm/ <ref>Pronounced yoo'nànŏk`tēàm at Columbia Encyclopedia</ref>) is the temporary IUPAC name for the superheavy element 118. It has the temporary IUPAC element symbol Uuo and has an atomic number of 118. It probably shares similar properties of its group, the noble gases, resembling radon in its chemical properties, and so some researchers have referred to it as eka-radon. It is probably the second radioactive gaseous element and the first standard semiconductive gas.

Ignoring nuclear instability due to radioactivity, scientists expect that ununoctium is much more chemically reactive than xenon or radon. It would likely form stable oxides (UuoO₃, etc.) as well as chlorides and fluorides.

[edit] History

The name ununoctium is used as a placeholder, as in scientific articles about the search for element 118. Transuranic elements (those beyond uranium) are, except for microscopic quantities, always artificially produced, and usually end up being named for a scientist or the location of a laboratory that does work in atomic physics (see systematic element name for more information). In 1999, researchers at Lawrence Berkeley National Laboratory announced the discovery of elements 116 and 118, in a paper published in Physical Review Letters. <ref>Ninov, Viktor, K. E. Gregorich, W. Loveland, A. Ghiorso, D. C. Hoffman, D. M. Lee, H. Nitsche, W. J. Swiatecki, U. W. Kirbach, C. A. Laue, J. L. Adams, J. B. Patin, D. A. Shaughnessy, D. A. Strellis, and P. A. Wilk (1999-05-27). "Observation of Superheavy Nuclei Produced in the Reaction of ⁸⁶Kr with ²⁰⁸Pb". Physical Review Letters 83 (6-9): 1104–1107. DOI:10.1103/PhysRevLett.83.1104. Retrieved on 2006-10-20.</ref>

The researchers claimed to have performed the reaction:

<math>\,^{86}_{36}\mathrm{Kr} + \,^{208}_{82}\mathrm{Pb} \, \to \,^{293}_{118}\mathrm{Uuo} + 1 \; ^1_0\mathrm{n} \; </math>

The following year, they published a retraction after other researchers were unable to duplicate the results.<ref>Public Affairs Department. "Results of element 118 experiment retracted", Berkeley Lab, 2001-7-21. Retrieved on 2006-10-17.</ref> In June 2002, the director of the lab announced that the original claim of the discovery of these two elements had been based on data fabricated by principal author Victor Ninov.

The American group had intended to name it ghiorsium after Albert Ghiorso before having to retract their claim.

On October 10, 2006, researchers working at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, announced in Physical Review C that they had indirectly detected ununoctium-294 produced via collisions of californium-249 atoms and calcium-48 ions <ref>Sanderson, Katherine (17 October 2006). Heaviest element made - again. nature@news.com. Nature (journal). Retrieved on 2006-10-19.</ref><ref>Phil Schewe and Ben Stein (17 October 2006). Elements 116 and 118 Are Discovered. Physics News Update. American Institute of Physics. Retrieved on 2006-10-19.</ref>:

<math>\,^{249}_{98}\mathrm{Cf} + \,^{48}_{20}\mathrm{Ca} \, \to \,^{294}_{118}\mathrm{Uuo} + 3 \; ^1_0\mathrm{n} \; </math>

The research team consisted of workers from JINR and the Lawrence Livermore National Laboratory in California, USA. The decay products of three atoms of ununoctium, not the atoms themselves, were observed in Dubna. A half-life of 0.89 ms was observed: ²⁹⁴Uuo decays into ²⁹⁰Uuh by alpha decay. ²⁹⁰Uuh is very unstable, decaying within a fraction of a second into ²⁸⁶Uuq, which may undergo spontaneous fission or undergo alpha decay into ²⁸²Uub, which will undergo spontaneous fission. <ref>Oganessian, Yu. Ts., Utyonkov, V.K.; Lobanov, Yu.V.; Abdullin, F.Sh.; Polyakov, A.N.; Sagaidak, R.N.; Shirokovsky, I.V.; Tsyganov, Yu.S.; Voinov, Yu.S.; Gulbekian, G.G.; Bogomolov, S.L.; B. N. Gikal, A. N. Mezentsev, S. Iliev; Subbotin, V.G.; Sukhov, A.M.; Subotic, K; Zagrebaev, V.I.; Vostokin, G.K.; Itkis, M. G.; Moody, K.J; Patin, J.B.; Shaughnessy, D.A.; Stoyer, M.A.; Stoyer, N.J.; Wilk, P.A.; Kenneally, J.M.; Landrum, J.H.; Wild, J.H.; and Lougheed, R.W. (2006-10-09). "Synthesis of the isotopes of elements 118 and 116 in the ²⁴⁹Cf and ²⁴⁵Cm+⁴⁸Ca fusion reactions". Physical Review C 74 (4): 044602. DOI:10.1103/PhysRevC.74.044602. Retrieved on 2006-10-16.</ref>