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Unbinilium

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Unbinilium, 120Ubn
Theoretical element
Unbinilium
Pronunciation/ˌuːnbaɪˈnɪliəm/ ​(OON-by-NIL-ee-əm)
Alternative nameselement 120, eka-radium
Unbinilium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ununennium Unbinilium
Unquadtrium Unquadquadium Unquadpentium Unquadhexium Unquadseptium Unquadoctium Unquadennium Unpentnilium Unpentunium Unpentbium Unpenttrium Unpentquadium Unpentpentium Unpenthexium Unpentseptium Unpentoctium Unpentennium Unhexnilium Unhexunium Unhexbium Unhextrium Unhexquadium Unhexpentium Unhexhexium Unhexseptium Unhexoctium Unhexennium Unseptnilium Unseptunium Unseptbium
Unbiunium Unbibium Unbitrium Unbiquadium Unbipentium Unbihexium Unbiseptium Unbioctium Unbiennium Untrinilium Untriunium Untribium Untritrium Untriquadium Untripentium Untrihexium Untriseptium Untrioctium Untriennium Unquadnilium Unquadunium Unquadbium
Ra
↑
Ubn
↓
—
ununennium ← unbinilium → unbiunium
Atomic number (Z)120
Groupgroup 2 (alkaline earth metals)
Periodperiod 8 (theoretical, extended table)
Block  s-block
Electron configuration[Og] 8s2 (predicted)[1]
Electrons per shell2, 8, 18, 32, 32, 18, 8, 2 (predicted)
Physical properties
Phase at STPsolid (predicted)[1][2]
Melting point953 K ​(680 °C, ​1256 °F) (predicted)[1]
Boiling point1973 K ​(1700 °C, ​3092 °F) (predicted)[3]
Density (near r.t.)7 g/cm3 (predicted)[1]
Heat of fusion8.03–8.58 kJ/mol (extrapolated)[2]
Atomic properties
Oxidation statescommon: (none)
(+2),[4] (+4), (+6)[1][5]
ElectronegativityPauling scale: 0.91 (predicted)[6]
Ionization energies
  • 1st: 563.3 kJ/mol (predicted)[7]
  • 2nd: 895–919 kJ/mol (extrapolated)[2]
Atomic radiusempirical: 200 pm (predicted)[1]
Covalent radius206–210 pm (extrapolated)[2]
Other properties
Crystal structure ​body-centered cubic (bcc)
Body-centered cubic crystal structure for unbinilium

(extrapolated)[8]
CAS Number54143-58-7
History
NamingIUPAC systematic element name
Isotopes of unbinilium
Experiments and theoretical calculations
| references

Unbinilium /uːnbaɪˈnɪliəm/, also known as eka-radium or simply element 120, is the temporary, systematic element name of a hypothetical chemical element in the periodic table with the temporary symbol Ubn and the atomic number 120. Unbinilium and Ubn are the temporary systematic IUPAC name and symbol, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkaline earth metal, and the second element in the eighth period.

To date, all attempts to synthesize this element have been unsuccessful. Its position as the seventh alkaline earth metal suggests that it would have similar properties to the alkaline earth metals, beryllium, magnesium, calcium, strontium, barium, and radium; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, unbinilium is expected to be less reactive than barium and radium and be closer in behavior to strontium, and while it should show the characteristic +2 oxidation state of the alkaline earth metals, it is also predicted to show the +4 oxidation state unknown in any other alkaline earth metal.

Attempts at synthesis

Neutron evaporation

Following their success in obtaining ununoctium by the reaction between 249Cf and 48Ca, the team at the Joint Institute for Nuclear Research (JINR) in Dubna started similar experiments in hope of creating unbinilium (element 120) from nuclei of 58Fe and 244Pu.[9] Isotopes of unbinilium are predicted to have alpha decay half-lives of the order of microseconds.[10][11] In March–April 2007, the synthesis of unbinilium was attempted at the JINR by bombarding a plutonium-244 target with iron-58 ions.[12] Initial analysis revealed that no atoms of element 120 were produced providing a limit of 400 fb for the cross section at the energy studied.[13]

The Russian team are planning to upgrade their facilities before attempting the reaction again.[14]

In April 2007, the team at GSI attempted to create unbinilium using uranium-238 and nickel-64:[14]

No atoms were detected providing a limit of 1.6 pb on the cross section at the energy provided. The GSI repeated the experiment with higher sensitivity in three separate runs from April–May 2007, Jan–March 2008, and Sept–Oct 2008, all with negative results and providing a cross section limit of 90 fb.[14]

In June–July 2010, scientists at the GSI attempted the fusion reaction:[14]

They were unable to detect any atoms, but exact details are not currently available.[14]

In August–October 2011, a different team at the GSI using the TASCA facility tried the new reaction:[14]

Results from this experiment are not yet available.[14]

Compound nucleus fission

Unbinilium is of interest because it is part of the hypothesized island of stability, with the compound nucleus 302Ubn being the most stable of those that can be created directly by current methods. It has been calculated that Z=120 may in fact be the next proton magic number, rather than at Z=114 or 126.

Several experiments have been performed between 2000–2008 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus 302Ubn. Two nuclear reactions have been used, namely 244Pu+58Fe and 238U+64Ni. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as 132Sn (Z=50, N=82). It was also found that the yield for the fusion-fission pathway was similar between 48Ca and 58Fe projectiles, indicating a possible future use of 58Fe projectiles in superheavy element formation.[15]

In 2008, the team at GANIL, France, described the results from a new technique which attempts to measure the fission half-life of a compound nucleus at high excitation energy, since the yields are significantly higher than from neutron evaporation channels. It is also a useful method for probing the effects of shell closures on the survivability of compound nuclei in the super-heavy region, which can indicate the exact position of the next proton shell (Z=114, 120, 124, or 126). The team studied the nuclear fusion reaction between uranium ions and a target of natural nickel:

The results indicated that nuclei of unbinilium were produced at high (~70 MeV) excitation energy which underwent fission with measurable half-lives > 10−18 s. Although very short (indeed, insufficient for the element to be considered by IUPAC to exist), the ability to measure such a process indicates a strong shell effect at Z=120. At lower excitation energy (see neutron evaporation), the effect of the shell will be enhanced and ground-state nuclei can be expected to have relatively long half-lives. This result could partially explain the relatively long half-life of 294Uuo measured in experiments at Dubna. Similar experiments have indicated a similar phenomenon at Z=124 (see unbiquadium) but not for flerovium, suggesting that the next proton shell does in fact lie at Z>120.[16][17]

Future reactions

The team at RIKEN have begun a program utilizing 248Cm targets and have indicated future experiments to probe the possibility of Z=120 being the next magic number using the aforementioned nuclear reactions to form 302Ubn.[18]

Calculated decay characteristics

In a quantum tunneling model with mass estimates from a macroscopic-microscopic model, the alpha-decay half-lives of several unbinilium isotopes (292–304Ubn) have been predicted to be around 1–20 microseconds.[19][20][21][22]

Extrapolated chemical properties

Unbinilium should be highly reactive, according to periodic trends, as this element is in the same periodic table column as the alkaline earth metals. It would be much more reactive than any other lighter elements of this group. If group reactivity is followed, this element would react violently in air to form an oxide (UbnO), in water to form the hydroxide, which would be a strong base and highly explosive in terms of flammability, and with the halogens to form salts (such as UbnCl2).[23]

Although unbinilium is expected to behave typically for an alkaline earth metal, showing a strong +2 oxidation state, the energetic properties of its valence electrons would increase its ionization energies; hence, unbinilium may have a lower metallic and ionic radius than expected, and may behave more similarly to calcium and strontium than barium or radium.[24] Unbinilium is also predicted to be the first alkaline earth metal to display the +4 oxidation state, due to the ionization energy of the 7p3/2 electrons, which is predicted to be very low.[1] The +1 state may also be stable in isolation.[4]

Target-projectile combinations leading to Z=120 compound nuclei

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with an atomic number of 120.

Target Projectile CN Attempt result
208Pb 88Sr 296Ubn Reaction yet to be attempted[1]
238U 64Ni 302Ubn Failure to date, σ < 94 fb
244Pu 58Fe 302Ubn Failure to date, σ < 0.4 pb
248Cm 54Cr 302Ubn Failure to date, not all details available
250Cm 54Cr 304Ubn Reaction yet to be attempted
249Cf 50Ti 299Ubn Results are not yet available
252Cf 50Ti 302Ubn Reaction yet to be attempted
257Fm 48Ca 305Ubn Reaction yet to be attempted

Theoretical calculations on evaporation cross sections

The below table contains various targets-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 = dinuclear system; AS = advanced statistical; σ = cross section

Target Projectile CN Channel (product) ~σmax Model Ref
208Pb 88Sr 296Ubn 1n (295Ubn) 70 fb DNS [25]
208Pb 87Sr 295Ubn 1n (294Ubn) 80 fb DNS [25]
208Pb 88Sr 296Ubn 1n (295Ubn) <0.1 fb MD [26]
238U 64Ni 302Ubn 3n (299Ubn) 3 fb MD [26]
238U 64Ni 302Ubn 2n (300Ubn) 0.5 fb DNS [27]
238U 64Ni 302Ubn 4n (298Ubn) 2 ab DNS-AS [28]
244Pu 58Fe 302Ubn 4n (298Ubn) 5 fb MD [26]
244Pu 58Fe 302Ubn 3n (299Ubn) 8 fb DNS-AS [28]
248Cm 54Cr 302Ubn 3n (299Ubn) 10 pb DNS-AS [28]
248Cm 54Cr 302Ubn 4n (298Ubn) 30 fb MD [26]
249Cf 50Ti 299Ubn 4n (295Ubn) 45 fb MD [26]
249Cf 50Ti 299Ubn 3n (296Ubn) 40 fb MD [26]
257Fm 48Ca 305Ubn 3n (302Ubn) 70 fb DNS [27]

See also

References

  1. ^ a b c d e f g h Hoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 978-1-4020-3555-5.
  2. ^ a b c d Bonchev, Danail; Kamenska, Verginia (1981). "Predicting the properties of the 113-120 transactinide elements". Journal of Physical Chemistry. 85 (9). American Chemical Society: 1177–1186. doi:10.1021/j150609a021.
  3. ^ Fricke, B.; Waber, J. T. (1971). "Theoretical Predictions of the Chemistry of Superheavy Elements" (PDF). Actinides Reviews. 1: 433–485. Retrieved 7 August 2013.
  4. ^ a b Thayer, John S. (2010). "Relativistic Effects and the Chemistry of the Heavier Main Group Elements". Relativistic Methods for Chemists. Challenges and Advances in Computational Chemistry and Physics. 10: 84. doi:10.1007/978-1-4020-9975-5_2. ISBN 978-1-4020-9974-8.
  5. ^ Cao, Chang-Su; Hu, Han-Shi; Schwarz, W. H. Eugen; Li, Jun (2022). "Periodic Law of Chemistry Overturns for Superheavy Elements". ChemRxiv (preprint). doi:10.26434/chemrxiv-2022-l798p. Retrieved 16 November 2022.
  6. ^ Pershina, V.; Borschevsky, A.; Anton, J. (2012). "Theoretical predictions of properties of group-2 elements including element 120 and their adsorption on noble metal surfaces". The Journal of Chemical Physics. 136 (134317). doi:10.1063/1.3699232. This article gives the Mulliken electronegativity as 2.862, which has been converted to the Pauling scale via χP = 1.35χM1/2 − 1.37.
  7. ^ Pershina, Valeria. "Theoretical Chemistry of the Heaviest Elements". In Schädel, Matthias; Shaughnessy, Dawn (eds.). The Chemistry of Superheavy Elements (2nd ed.). Springer Science & Business Media. p. 154. ISBN 9783642374661.
  8. ^ Seaborg, Glenn T. (1969). "Prospects for further considerable extension of the periodic table" (PDF). Journal of Chemical Education. 46 (10): 626–634. doi:10.1021/ed046p626. Retrieved 22 February 2018.
  9. ^ "A New Block on the Periodic Table" (PDF). Lawrence Livermore National Laboratory. April 2007. Retrieved 2008-01-18.
  10. ^ Chowdhury, P. Roy; Samanta, C.; Basu, D. N. (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Physical Reviews C. 77 (4): 044603. arXiv:0802.3837. Bibcode:2008PhRvC..77d4603C. doi:10.1103/PhysRevC.77.044603.
  11. ^ Chowdhury, R. P.; Samanta, C.; Basu, D.N. (2008). "Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130". At. Data & Nucl. Data Tables. 94 (6): 781–806. arXiv:0802.4161. Bibcode:2008ADNDT..94..781C. doi:10.1016/j.adt.2008.01.003.
  12. ^ Synthesis of New Nuclei and Study of Nuclear Properties and Heavy-Ion Reaction Mechanisms. jinr.ru
  13. ^ Oganessian, Yu.Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Sagaidak, R.; Shirokovsky, I.; Tsyganov, Yu.; et al. (2009). "Attempt to produce element 120 in the 244Pu+58Fe reaction". Phys. Rev. C. 79 (2): 024603. Bibcode:2009PhRvC..79b4603O. doi:10.1103/PhysRevC.79.024603.
  14. ^ a b c d e f g Cite error: The named reference Duellmann was invoked but never defined (see the help page).
  15. ^ see Flerov lab annual reports 2000–2004
  16. ^ Natowitz, Joseph (2008). "How stable are the heaviest nuclei?". Physics. 1: 12. Bibcode:2008PhyOJ...1...12N. doi:10.1103/Physics.1.12.
  17. ^ Morjean, M.; Jacquet, D.; Charvet, J.; l’Hoir, A.; Laget, M.; Parlog, M.; Chbihi, A.; Chevallier, M.; et al. (2008). "Fission Time Measurements: A New Probe into Superheavy Element Stability". Phys. Rev. Lett. 101 (7): 072701. Bibcode:2008PhRvL.101g2701M. doi:10.1103/PhysRevLett.101.072701. PMID 18764526.
  18. ^ see slide 11 in Future Plan of the Experimental Program on Synthesizing the Heaviest Element at RIKEN
  19. ^ P. Roy Chowdhury; C. Samanta; D. N. Basu (2006). "α decay half-lives of new superheavy elements". Phys. Rev. C. 73: 014612. arXiv:nucl-th/0507054. Bibcode:2006PhRvC..73a4612C. doi:10.1103/PhysRevC.73.014612. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  20. ^ Samanta, C.; Chowdhury, P. Roy; Basu, D.N. (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A. 789: 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  21. ^ Chowdhury, P. Roy; Samanta, C.; Basu, D. N. (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Phys. Rev. C. 77 (4): 044603. arXiv:0802.3837. Bibcode:2008PhRvC..77d4603C. doi:10.1103/PhysRevC.77.044603. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  22. ^ Chowdhury, P. Roy; Samanta, C.; Basu, D. N. (2008). "Nuclear half-lives for α-radioactivity of elements with 100 ≤ Z ≤ 130". At. Data & Nucl. Data Tables. 94 (6): 781–806. arXiv:0802.4161. Bibcode:2008ADNDT..94..781C. doi:10.1016/j.adt.2008.01.003. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  23. ^ Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. p. 586. ISBN 978-0-19-960563-7.
  24. ^ Seaborg (c. 2006). "transuranium element (chemical element)". Encyclopædia Britannica. Retrieved 2010-03-16.
  25. ^ a b Feng, Zhao-Qing; Jin, Gen-Ming; Li, Jun-Qing; Scheid, Werner (2007). "Formation of superheavy nuclei in cold fusion reactions". Physical Review C. 76 (4): 044606. arXiv:0707.2588. Bibcode:2007PhRvC..76d4606F. doi:10.1103/PhysRevC.76.044606.
  26. ^ a b c d e f Zagebraev, V; Greiner, W (2008). "Synthesis of superheavy nuclei: A search for new production reactions". Physical Review C. 78 (3): 034610. arXiv:0807.2537. Bibcode:2008PhRvC..78c4610Z. doi:10.1103/PhysRevC.78.034610.
  27. ^ 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. arXiv:0803.1117. Bibcode:2009NuPhA.816...33F. doi:10.1016/j.nuclphysa.2008.11.003.
  28. ^ a b c Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Manganaro, M.; Hanappe, F.; Heinz, S.; Hofmann, S.; Muminov, A.; et al. (2009). "Quasifission and fusion-fission in reactions with massive nuclei: Comparison of reactions leading to the Z=120 element". Physical Review C. 79 (2): 024606. arXiv:0812.4410. Bibcode:2009PhRvC..79b4606N. doi:10.1103/PhysRevC.79.024606.
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