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Ununhexium

 116 ununpentium ← ununhexium → ununseptium Po↑Uuh↓(Uhh)
General
Name, Symbol, Number ununhexium, Uuh, 116
Chemical series presumably poor metals
Group, Period, Block 16, 7, p
Standard atomic weight (302)  g·mol−1
Electron configuration perhaps [Rn] 5f14 6d10 7s2 7p4
(guess based on polonium)
Electrons per shell 2, 8, 18, 32, 32, 18, 6
CAS registry number 54100-71-9
Selected isotopes
Main article: Isotopes of ununhexium
iso NA half-life DM DE (MeV) DP
293Uuh syn 61 ms
References

Ununhexium (pronounced /ˌjuːnənˈhɛksiəm/) is the temporary name of a synthetic superheavy element in the periodic table that has the temporary symbol Uuh and has the atomic number 116. Some research has referred to it as "eka-polonium".

Discovery

In December, 2000 the Joint Institute for Nuclear Research (Dubna, Russia) published results[1] that described the discovery in 2000 of decay of the isotope 292Uuh, which was produced in the reaction of 248Cm with 48Ca (curium and calcium, elements 96 and 20, respectively). It has a half-life of about 18 milliseconds (0.018 seconds) and decayed into 288Uuq (ununquadium, element 114). On May 112001, the institute reported synthesizing a second atom, and that the properties confirmed a region of "enhanced" stability (see Island of stability).

In 2004 in the Joint Institute for Nuclear Research the synthesis of this element was confirmed by another method (the chemical identifying on final products of decay of element).

Further research

Ununhexium is a temporary IUPAC systematic element name.

In October, 2006 it was announced that on three occasions californium-249 atoms had been bombarded with calcium-48 ions to produce ununoctium (element 118), which decayed to ununhexium within a millisecond.[2] If confirmed, the synthesis of element 116 will have been proven definitively.

The reaction that created ununhexium is:

$\,^{248}_{96}\mathrm{Cm} + \,^{48}_{20}\mathrm{Ca} \, \to \,^{292}_{116}\mathrm{Uuh} + 4 \; ^1_0\mathrm{n} \;$

This decayed 47 milliseconds later as follows to a previously identified isotope of element 114, Uuq.

$\,^{292}_{116}\mathrm{Uuh} \to \,^{288}_{114}\mathrm{Uuq} \, + \,^{4}_{2}\mathrm{He} \;$

History

In 1999, researchers at Lawrence Berkeley National Laboratory announced the discovery of elements 116 and 118 (ununhexium and ununoctium), in a paper published in Physical Review Letters.[3] The following year, they published a retraction after other researchers were unable to duplicate the results.[4] 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 the principal author Victor Ninov.

References

1. ^ Oganessian, Yu. Ts.; et al. (2000). "Observation of the decay of 292116". Physical Review C 63: 011301. doi:10.1103/PhysRevC.63.011301.
2. ^ Oganessian, Yu. Ts.; et al. (2006). "Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm+48Ca fusion reactions". Physical Review C 74: 044602. doi:10.1103/PhysRevC.74.044602.
3. ^ Ninov, V.; et al. (1999). "Observation of Superheavy Nuclei Produced in the Reaction of 86Kr with 208Pb". Physical Review Letters 83: 1104. doi:10.1103/PhysRevLett.83.1104.
4. ^ Editorial note on the preceding.