Elemnt 120
The new horizons in science mean new inventions and even new elements to be found. The modern techniques make the last thing not a dream but reality. In 2006 the scientific community has been prizing Russian and US scientist for their success in identification of 118th element (LeClair, 2006), which was the newest super-heavy element. This was performed on the in Dubna, Russia through observation of atomic decay, indicating that the observed element 116 was produced via the alpha decay of element 118. This is was the second data this element was declared to be synthesized, but this time the data were solid and no one could accuse the researcher of any possible falsification. It was acknowledged by the IUPAC and given a temporary name ununoctium.
The next step was to synthesize the element 120 within next year, but what was so easy to turned out to be a much harder problem to be solved within days and even years. This element has been predicted to undergo alpha decay with half-lives of the order of microseconds. However, the stability assessment in the region Z=120, N=184 is not exceptionally high with respect to the neighboring regions. That was not that much optimistic, but still does not theoretically argued the possibility of its existence.
GSI investigations leading to the element Z=120 were considering three different projectile-target combinations all leading to the same compound nucleus 302120 or 302Ubn:
64Ni + 238U
58Fe + 244Pu, and
54Cr + 248Cm
The neutron number of the compound nucleus 302120 is N=182. This is only 2 neutrons below N=184 where the neutron shell closure is expected. Therefore, 302120 or 302Ubn is closer to the N=184 shell than any other so far produced compound nucleus with lower Z.
In March–April 2007, the synthesis of unbinilium was attempted at the JINR by bombarding a plutonium-244 target with iron-58 ions, this attempt was unsusessful ansd showed lack in energy.
The largest production rate for Z=120 is predicted for the most mass asymmetric projectile/target combination 54Cr + 248Cm. However, at SHIP this experiment was not possible so the reaction 64Ni + 238U was studied. If the proton shell closure is at Z=120 then an enhanced production rate and half-live of the element 120 would be expected. Depending on the magnitude of the stabilization due to the closed shell, one could expect up to a few events per week for the isotopes 299120 and 298120 produced in 64Ni + 238U reactions. Though the half-lives are expected to be of the order of some 10 μs, that is enough for detection, it has been 9 years, but all attempts were unsuccessful, though this phantom element was already named unbinilium or eka-radium.
Conclusion
As all attempts to synthesize the Unbinilium or eka-radium, better known as element 120 in the Periodical Table, the element 118 named Ununoctium is currently the last known element and well as the heaviest one.
The chemist and physicists are not giving up and trying to establish amiable way to synthesize a new super-heavy element and to prove its existence to the whole World. The proton number which defines the location of the "island of stability" (the region where it is possible for atoms to exist) is still unclear. Various theoretical models suggest numbers of Z=114, 120 or 126. So may be the next success will come with element 126 or 114.
References
LeClaire, J. US, Russian Scientists Create Super-Heavy Element 118. Web. 11 February 2016. Retrieved from http://www.technewsworld.com/story/53713.html
Approaches to element 120 (unbinilium) Web. 11 February 2016. Retrieved from https://www.webelements.com/nexus/chemistry/approaches-element-120-unbinilium
A New Block on the Periodic Table" Lawrence Livermore National Laboratory. April 2007. Web. 11 February 2016. Retrieved from
Hofmann, Sigurd (2013). Overview and Perspectives of SHE Research at GSI SHIP. p.23–32
