Ununpentium

Ununpentium (pronounced /uːnuːnˈpɛntiəm/ ( listen)[1] oon-oon-PEN-tee-əm) is the temporary name of a synthetic superheavy element in the periodic table that has the temporary symbol Uup and has the atomic number 115.

It is placed as the heaviest member of group 15 (VA) although a sufficiently stable isotope is not known at this time that would allow chemical experiments to confirm its position. It was first observed in 2003 and only about 30 atoms of ununpentium have been synthesized to date, with just 4 direct decays of the parent element having been detected. Four consective isotopes are currently known, 287-290Uup, with 289Uup having the longest measured half-life of ~220 ms, although the isotope 290Uup may well have an even longer half-life (only a single decay has been measured leading to poor accuracy).

History
Discovery profile

On February 2, 2004, synthesis of ununpentium was reported in Physical Review C by a team composed of Russian scientists at the Joint Institute for Nuclear Research in Dubna, and American scientists at the Lawrence Livermore National Laboratory.[2][3] The team reported that they bombarded americium-243 with calcium-48 ions to produce four atoms of ununpentium. These atoms, they report, decayed by emission of alpha-particles to ununtrium in approximately 100 milliseconds.

4820Ca + 24395Am → 291115Uup* → 288115Uup

The Dubna-Livermore collaboration has strengthened their claim for the discovery of ununpentium by conducting chemical experiments on the decay daughter 268Db. In experiments in June 2004 and December 2005, the Dubnium isotope was successfully identified by milking the Db fraction and measuring any SF activities.[4][5] Both the half-life and decay mode were confirmed for the proposed 268Db which lends support to the assignment of Z=115 to the parent nuclei.
Official claim of discovery of ununpentium

Sergei Dmitriev from the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna, Russia, has formally put forward their claim of discovery of ununpentium to the Joint Working Party (JWP) from IUPAC and IUPAP.[6] The JWP are expected to publish their opinions on such claims in the near future.[citation needed]
Naming

Ununpentium is historically known as eka-bismuth. Ununpentium is a temporary IUPAC systematic element name. Research scientists usually refer to the element simply as element 115.
Future experiments

As a primary next-goal for the Dubna team, they are planning to examine two products of the 243Am + 48Ca using mass spectrometry in their state-of-the-art MASHA machine. They will attempt to isolate the dubnium products, convert them chemically into a volatile compound, most likely 268DbCl5, and measure the mass directly.

The FLNR also have future plans to study light isotopes of element 115 using the reaction 241Am + 48Ca.[7]
Isotopes and nuclear properties
Nucleosynthesis
Target-projectile combinations leading to Z=115 compound nuclei

The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=115.
Target Projectile CN Attempt result
208Pb 75As 283Uup Reaction yet to be attempted
232Th 55Mn 287Uup Reaction yet to be attempted
238U 51V 289Uup Failure to date
237Np 50Ti 287Uup Reaction yet to be attempted
244Pu 45Sc 289Uup Reaction yet to be attempted
243Am 48Ca 291Uup Successful reaction
241Am 48Ca 289Uup Reaction yet to be attempted
248Cm 41K 289Uup Reaction yet to be attempted
249Bk 40Ar 289Uup Reaction yet to be attempted
249Cf 37Cl 286Uup Reaction yet to be attempted
Hot fusion

This section deals with the synthesis of nuclei of ununpentium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40-50 MeV, hence "hot"), leading to a reduced probability of survival from fission. The excited nucleus then decays to the ground state via the emission of 3-5 neutrons. Fusion reactions utilizing 48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30-35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.
238U(51V,xn)289−xUup

There are strong indications that this reaction was performed in late 2004 as part of a uranium(IV) fluoride target test at the GSI. No reports have been published suggesting that no products atoms were detected, as anticipated by the team.[8]
243Am(48Ca,xn)291−xUup (x=3,4)

This reaction was first performed by the team in Dubna in July-August 2003. In two separate runs they were able to detect 3 atoms of 288Uup and a single atom of 287Uup. The reaction was studied further in June 2004 in an attempt to isolate the descendant 268Db from the 288Uup decay chain. After chemical separation of a +4/+5 fraction, 15 SF decays were measured with a lifetime consistent with 268Db. In order to prove that the decays were from dubnium-268, the team repeated the reaction in August 2005 and separated the +4 and +5 fractions and further separated the +5 fractions into tantalum-like and niobium-like ones. Five SF activities were observed, all occurring in the +5 fractions and none in the tantalum-like fractions, proving that the product was indeed isotopes of dubnium.
Chronology of isotope discovery
Isotope Year discovered Discovery reaction
287Uup 2003 243Am(48Ca,4n)
288Uup 2003 243Am(48Ca,3n)
289Uup 2009 249Bk(48Ca,4n)
290Uup 2009 249Bk(48Ca,3n)
Yields of isotopes
Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing ununpentium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.
Projectile Target CN 2n 3n 4n 5n
48Ca 243Am 291Uup 3.7 pb, 39.0 MeV 0.9 pb, 44.4 MeV
Theoretical calculations
Decay characteristics

Theoretical calculations using a quantum-tunneling model support the experimental alpha-decay half-lives.[9]
Evaporation residue cross sections

The table below contains various target-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

MD = multi-dimensional; DNS = Di-nuclear system; σ = cross section
Target Projectile CN Channel (product) σmax Model Ref
243Am 48Ca 291Uup 3n (288Uup) 3 pb MD [10]
243Am 48Ca 291Uup 4n (287Uup) 2 pb MD [10]
243Am 48Ca 291Uup 3n (288Uup) 1 pb DNS [11]
242Am 48Ca 290Uup 3n (287Uup) 2.5 pb DNS [11]
Chemical properties
Extrapolated chemical properties
Oxidation states

Ununpentium is projected to be the third member of the 7p series of non-metals and the heaviest member of group 15 (VA) in the Periodic Table, below bismuth. In this group, each member is known to portray the group oxidation state of +V but with differing stability. For nitrogen, the +V state is very difficult to achieve due to the lack of low-lying d-orbitals and the inability of the small nitrogen atom to accommodate five ligands. The +V state is well represented for phosphorus, arsenic, and antimony. However, for bismuth it is rare due to the reluctance of the 6s2 electron to participate in bonding. This effect is known as the "inert pair effect" and is commonly linked to relativistic stabilisation of the 6s-orbitals. It is expected that ununpentium will continue this trend and portray only +III and +I oxidation states. Nitrogen(I) and bismuth(I) are known but rare and Uup(I) is likely to show some unique properties.[12]
Chemistry

It is expected that the chemistry of ununpentium will be related to its lighter homologue bismuth. In this regard it is expected to undergo oxidation only as far as the trioxide Uup2O3. Oxidation with the more reactive halogens should form the trihalides, such as UupF3 and UupCl3. The less-oxidizing, heavier halogens may be able to promote only the formation of the monohalides, UupBr and UupI.
Fictional uses

* Some UFOlogists believe that a stable room temperature isotope of ununpentium exists, and that it functions as the fuel for an anti-gravity engine used by alien flying saucers. This claim was initially made in 1989, about 14 years before ununpentium was first synthesized.
* Ununpentium is the power source for the Back Step system in the American television series Seven Days.
* Elerium-115 serves as the power source for alien technologies in the X-COM video game series.
* Ununpentium is featured in Call of Duty: World at War in the side-campaign Nazi Zombies. In it, ununpentium is used for multiple reasons, being used to power weapons, teleporters, and even creating the zombies themselves.

See also
Chemistry portal

* Island of stability

References

1. ^ J. Chatt (1979). "Recommendations for the Naming of Elements of Atomic Numbers Greater than 100". Pure Appl. Chem. 51: 381–384. doi:10.1351/pac197951020381.
2. ^ Oganessian, Yu. Ts.; Utyonkoy, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G. et al. (2004). "Experiments on the synthesis of element 115 in the reaction 243Am(48Ca,xn)291?x115". Physical Review C 69: 021601. doi:10.1103/PhysRevC.69.021601.
3. ^ Oganessian et al. (2003). "Experiments on the synthesis of element 115 in the reaction 243Am(48Ca,xn)291−x115""]. JINR preprints. http://www.jinr.ru/publish/Preprints/2003/178(E7-2003-178).pdf.
4. ^ Oganessian et al. (2004). "Results of the experiment on chemical identification of db as a decay product of element 115". JINR preprints. http://www.jinr.ru/publish/Preprints/2004/157(e12-2004-157).pdf.
5. ^ Oganessian, Yu. Ts. (2005). "Synthesis of elements 115 and 113 in the reaction ^{243}Am+^{48}Ca". Physical Review C 72: 034611. doi:10.1103/PhysRevC.72.034611.
6. ^ "Project: Priority claims for the discovery of elements with atomic number greater than 111". IUPAC. http://www.iupac.org/web/ins/2006-046-1-200. Retrieved 2009-07-07.
7. ^ "Study of heavy and superheavy nuclei (see experiment 1.5)". http://flerovlab.jinr.ru/flnr/education_list.html.
8. ^ "List of experiments 2000-2006". http://opal.dnp.fmph.uniba.sk/~beer/experiments.php.
9. ^ C. Samanta, P. Roy Chowdhury and D.N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A 789: 142–154. doi:10.1016/j.nuclphysa.2007.04.001.
10. ^ a b Zagrebaev, V (2004). "Fusion-fission dynamics of super-heavy element formation and decay". Nuclear Physics A 734: 164. doi:10.1016/j.nuclphysa.2004.01.025. http://nrv.jinr.ru/pdf_file/npa_04.pdf.
11. ^ a b Feng, Z; Jin, G; Li, J; Scheid, W (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A 816: 33. doi:10.1016/j.nuclphysa.2008.11.003. http://arxiv.org/pdf/0803.1117.
12. ^ Keller, O. L., Jr.; C. W. Nestor, Jr. (1974). "Predicted properties of the superheavy elements. III. Element 115, Eka-bismuth". Journal of Physical Chemistry 78: 1945. doi:10.1021/j100612a015.

External links

* Uut and Uup Add Their Atomic Mass to Periodic Table
* Superheavy elements
* History and etymology