UNUNOCTIUM

'Ununoctium' (IPA pronunciation: ^[1]) is the temporary IUPAC name for the superheavy element having atomic number of 118, currently the highest atomic number assigned to a reputedly discovered element. It has the temporary IUPAC element symbol 'Uuo'. It can also be called 'eka-radon' and only three atoms of this element have been detected. ^[2] The name ''ununoctium'' is a systematic element name, used as a placeholder until the IUPAC decides on a name.

Contents

Discovery

History

See also

References

External links

Discovery

On October 16, 2006, researchers working at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, announced in ''Physical Review C'' that they had indirectly detected a total of three nuclei of ununoctium-294 (one in 2002 and two more in 2005) produced via collisions of californium-249 atoms and calcium-48 ions ^[3][4]:
:$,^\{249\}\_\{98\}mathrm\{Cf\}\; +\; ,^\{48\}\_\{20\}mathrm\{Ca\}\; ,\; o\; ,\{\}^\{294\}\_\{118\}mathrm\{Uuo\}\; +\; 3\; ;\; ^1\_0mathrm\{n\}\; ;$
Because of the very small fusion reaction probability (the fusion cross section is 0.5 pb = 5×10⁻⁴¹ m²) more than 4×10¹⁹ calcium ions had to be shot at the californium to have only three fusion reactions.
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. Since there were only three nuclei, the half-life was derived from observed lifetimes and has a large uncertainty: 0.89_-0.31^+1.07 ms.
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,
:$,^\{245\}\_\{96\}mathrm\{Cm\}\; +\; ,^\{48\}\_\{20\}mathrm\{Ca\}\; ,\; o\; ,^\{290\}\_\{116\}mathrm\{Uuh\}\; +\; 3\; ;\; ^1\_0mathrm\{n\}\; ;$
and checking that the ²⁹⁰Uuh decay matched the decay chain of the ²⁹⁴Uuo nuclei.
The daughter nucleus ²⁹⁰Uuh is very unstable, decaying with a half-life of 14 milliseconds into ²⁸⁶Uuq, which may undergo spontaneous fission or undergo alpha decay into ²⁸²Uub, which will undergo spontaneous fission. ^[5]

History

In 1999, researchers at Lawrence Berkeley National Laboratory had announced the discovery of elements 116 and 118, in a paper published in ''Physical Review Letters''. ^[6]
The researchers claimed to have performed the reaction:
:$,^\{86\}\_\{36\}mathrm\{Kr\}\; +\; ,^\{208\}\_\{82\}mathrm\{Pb\}\; ,\; o\; ,^\{293\}\_\{118\}mathrm\{Uuo\}\; +\; ,^\{1\}\_\{0\}mathrm\{n\}\; ;$
The following year, they published a retraction after other researchers were unable to duplicate the results.^[7]
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.

See also

★ Discoveries of the chemical elements

★ Island of stability

References

1. Pronounced yoo'nànŏk`tēàm at Columbia Encyclopedia
2. The Top 6 Physics Stories of 2006 Stone, Alex
3. Heaviest element made - again
4. Elements 116 and 118 Are Discovered Phil Schewe and Ben Stein
5. Synthesis of the isotopes of elements 118 and 116 in the ²⁴⁹Cf and ²⁴⁵Cm+⁴⁸Ca fusion reactions, , Yu. Ts., Oganessian, Physical Review C,
6. Observation of Superheavy Nuclei Produced in the Reaction of ⁸⁶Kr with ²⁰⁸Pb, , Viktor, Ninov, Physical Review Letters,
7. Results of element 118 experiment retracted

External links

★ Livermore press release about discovery

★ WebElements.com - Uuo

★ Apsidium - Ununoctium

★ U.S., Russian scientists discover new element

★ Theory of atomic-mass calculation