Ununoctium is the temporary
IUPAC name[9] for the
transactinide element having the
atomic number 118 and temporary
element symbol Uuo. It is also known as
eka-radon or
element 118, and on the
periodic table of the elements it is a
p-block element and the last one of the
7th period. Ununoctium is currently the only
synthetic member of
Group 18. It has the highest atomic number and highest
atomic mass of all discovered elements.
The
radioactive ununoctium atom is very unstable, and since 2002, only three atoms (possibly four) of the isotope
294Uuo have been detected.
[10] While this allowed for very little experimental characterization of its properties and possible
compounds, theoretical calculations have resulted in many predictions, including some unexpected ones. For example, although ununoctium is a member of Group 18, it may possibly not be a
noble gas, unlike all the other Group 18 elements.
[1] It was formerly thought to be a gas but is now predicted to be a
solid under
normal conditions due to relativistic effects.
[1]
Unsuccessful attempts
In late 1998, Polish physicist Robert Smolańczuk published calculations on the fusion of atomic nuclei towards the synthesis of
superheavy atoms, including ununoctium.
[11] His calculations suggested that it might be possible to make ununoctium by fusing
lead with
krypton under carefully controlled conditions.
[11]
In 1999, researchers at
Lawrence Berkeley National Laboratory made use of these predictions and announced the discovery of
ununhexium and ununoctium, in a paper published in
Physical Review Letters,
[12] and very soon after the results were reported in
Science.
[13] The researchers claimed to have performed the
reaction
- 86 36Kr + 208 82Pb → 293 118Uuo + n.
The following year, they published a retraction after researchers at other laboratories were unable to duplicate the results and the Berkeley lab itself was unable to duplicate them as well.
[14] 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.
[15]
Discovery claims
The first decay of atoms of ununoctium was observed at the
Joint Institute for Nuclear Research (JINR) by Yuri Oganessian and his group in
Dubna, Russia, in 2002.
[16] On October 9, 2006, researchers from JINR and
Lawrence Livermore National Laboratory of California, USA, working at the JINR in
Dubna, announced
[7] that they had indirectly detected a total of three (possibly four) nuclei of ununoctium-294 (one or two in 2002
[17] and two more in 2005) produced via collisions of
californium-249 atoms and
calcium-48 ions:
[18][19][20][21][22]
In 2011, the IUPAC has evaluated the 2006 results of the Dubna-Livermore collaboration and concluded that they did not meet the criteria for discovery.
[23]
Because of the very small
fusion reaction probability (the fusion
cross section is ~0.3–0.6
pb = (3–6)×10
−41 m
2) the experiment took 4 months and involved a beam dose of 4×10
19 calcium ions that had to be shot at the
californium target to produce the first recorded event believed to be the synthesis of ununoctium.
[6] Nevertheless, researchers are highly confident that the results are not a
false positive, since the chance that the detections were random events was estimated to be less than one part in 100,000.
[24]
In the experiments, the alpha-decay of three atoms of ununoctium was observed. A fourth decay by direct
spontaneous fission was also proposed. A
half-life of 0.89 ms was calculated:
294Uuo decays into
290Uuh by
alpha decay. Since there were only three nuclei, the half-life derived from observed lifetimes has a large uncertainty: 0.89
+1.07
−0.31 ms.
[7]
- 294 118Uuo → 290 116Uuh + 4He
The identification of the
294Uuo nuclei was verified by separately creating the putative
daughter nucleus 290Uuh by means of a bombardment of
245Cm with
48Ca ions,
- 245 96Cm + 48 20Ca → 290 116Uuh + 3 n,
and checking that the
290Uuh decay matched the
decay chain of the
294Uuo nuclei.
[7] The daughter nucleus
290Uuh is very unstable, decaying with a half-life of 14 milliseconds into
286Uuq, which may experience either
spontaneous fission or alpha decay into
282Cn, which will undergo spontaneous fission.
[7]
In a quantum-tunneling model, the alpha decay half-life of
294Uuo was predicted to be 0.66
+0.23
−0.18 ms
[25] with the experimental Q-value published in 2004.
[26] Calculation with theoretical Q-values from the macroscopic-microscopic model of Muntian–Hofman–Patyk–Sobiczewski gives somewhat low but comparable results.
[27]
Following the success in obtaining ununoctium, the discoverers have started similar experiments in the hope of creating
unbinilium from
58Fe and
244Pu.
[28] Isotopes of unbinilium are predicted to have alpha decay half lives of the order of micro-seconds.
[29][30]
Hey friends Einstein had suggested that if we purify uranium-235 worlds best atomic bomb would be created but i suggest that if un-unoctium is purified worlds best atomic bomb would be created but it being a synthetic element the chances are too low
Source::http://en.wikipedia.org/wiki/Ununoctium