Unbinilium

Unbinilium, ₀₀Ubn
Unbinilium
Pronunciation	/ˌuːnbaɪˈnɪliəm/ (OON-by-NIL-ee-əm)
Unbinilium in the periodic table
	ununennium ← unbinilium → unbiunium
Group	group 2 (alkaline earth metals)
Period	period 8 (theoretical, extended table)
Block	s-block
Electron configuration	[Og] 8s2 (predicted)
Electrons per shell	2, 8, 18, 32, 32, 18, 8, 2; (predicted)
Physical properties
Phase at STP	unknown phase
Atomic properties
Oxidation states	common: (none); ( 2), ( 4), ( 6)
Isotopes of unbinilium ക; തി;
	Template:infobox unbinilium isotopes does not exist
	വർഗ്ഗം: Unbinilium; view; talk; edit; \| references

Unbinilium (pronounced /uːnbaɪˈnɪliəm/), also called eka-radium, is the temporary, systematic element name of a hypothetical chemical element in the periodic table that has the temporary symbol Ubn and has the atomic number 120. Since unbinilium is placed below the alkaline earth metals it possibly has properties similar to those of radium or barium.

Attempts to date to synthesize the element using fusion reactions at low excitation energy have met with failure, although there are reports that the fission of nuclei of element 120 at very high excitation has been successfully measured, indicating a strong shell effect at Z=120.

Attempts at synthesis

Neutron evaporation

In March-April 2007, the synthesis of element 120 was attempted at the Flerov Laboratory of Nuclear Reactions in Dubna by bombarding a plutonium-244 target with iron-58 ions.^[4] 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.^[5]

\,_{94}^{244}\mathrm {Pu}  \,_{26}^{58}\mathrm {Fe} \to \,_{120}^{302}\mathrm {Ubn} ^{*}\to \ fission\ only

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

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

\,_{92}^{238}\mathrm {U}  \,_{28}^{64}\mathrm {Ni} \to \,_{120}^{302}\mathrm {Ubn} ^{*}\to \ fission\ only

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.

Compound nucleus fission

Element 120 is of interest because it is part of the hypothesized island of stability, with the compound nucleus ³⁰²120 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 ³⁰²120. 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.^[6]

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:

\,_{92}^{238}\mathrm {U}  \,_{28}^{nat}\mathrm {Ni} \to \,^{296,298,299,300,302}\mathrm {120} ^{*}\to \ fission.

The results indicated that nuclei of element 120 were produced at high (~70 MeV) excitation energy which underwent fission with measurable half-lives > 10⁻¹⁸s. Although very short, 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 ²⁹⁴118 measured in experiments at Dubna (see ununoctium). Similar experiments have indicated a similar phenomenon at Z=124 (see unbiquadium) but not at Z = 114 (see ununquadium), suggesting that the next proton shell does in fact lie at Z>120.^[7]^[8]

Future reactions

The GSI have plans to start up a program utilizing ²⁴⁸Cm targets for SHE production and will most likely attempt this reaction in 2010 or 2011.^[9]

Likewise, the team at RIKEN have also 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 ³⁰²120.^[10]

Calculated decay characteristics

In a quantum tunneling model with mass estimates from a macroscopic-microscopic model, the alpha-decay half-lives of several isotopes of the element 120 (namely, ^292-304120) have been predicted to be around 1–20 microseconds.^[11]^[12]^[13]^[14]

Extrapolated reactivity

Unbinilium should be highly reactive, according to periodic trends, as this element is a member of 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) and in water to form the hydroxide, which would be a strong base and highly explosive in terms of flammability. It is also possible that, due to relativistic effects, the element has noble gas character, as already seen for element 114. A predicted oxidation state is II.

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 Z=120.

Target	Projectile	CN	Attempt result
²³²Th	⁷⁰Zn	³⁰²120	Reaction yet to be attempted
²³⁸U	⁶⁴Ni	³⁰²120	Failure to date, σ < 94 fb
²⁴⁴Pu	⁵⁸Fe	³⁰²120	Failure to date, σ < 0.4 pb
²⁴⁸Cm	⁵⁴Cr	³⁰²120	Reaction yet to be attempted
²⁴⁹Cf	⁵⁰Ti	²⁹⁹120	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)	~σ_max	Model	Ref
²⁰⁸Pb	⁸⁸Sr	²⁹⁶120	1n (²⁹⁵120)	70 fb	DNS	^[15]
²⁰⁸Pb	⁸⁷Sr	²⁹⁵120	1n (²⁹⁴120)	80 fb	DNS	^[15]
²⁰⁸Pb	⁸⁸Sr	²⁹⁶120	1n (²⁹⁵120)	<0.1 fb	MD	^[16]
²³⁸U	⁶⁴Ni	³⁰²120	3n (²⁹⁹120)	3 fb	MD	^[16]
²³⁸U	⁶⁴Ni	³⁰²120	2n (³⁰⁰120)	0.5 fb	DNS	^[17]
²³⁸U	⁶⁴Ni	³⁰²120	4n (²⁹⁸120)	2 ab	DNS-AS	^[18]
²⁴⁴Pu	⁵⁸Fe	³⁰²120	4n (²⁹⁸120)	5 fb	MD	^[16]
²⁴⁴Pu	⁵⁸Fe	³⁰²120	3n (²⁹⁹120)	8 fb	DNS-AS	^[18]
²⁴⁸Cm	⁵⁴Cr	³⁰²120	3n (²⁹⁹120)	10 pb	DNS-AS	^[18]
²⁴⁸Cm	⁵⁴Cr	³⁰²120	4n (²⁹⁸120)	30 fb	MD	^[16]
²⁴⁹Cf	⁵⁰Ti	²⁹⁹120	4n (²⁹⁵120)	45 fb	MD	^[16]
²⁴⁹Cf	⁵⁰Ti	²⁹⁹120	3n (²⁹⁶120)	40 fb	MD	^[16]
²⁵⁷Fm	⁴⁸Ca	³⁰⁵120	3n (³⁰²120)	70 fb	DNS	^[17]

References

↑ ^1.0 ^1.1 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.
↑ 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.
↑ 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.
↑ "THEME03-5-1004-94/2009". Archived from the original on 2008-05-11. Retrieved 2008-01-07.
↑ Oganessian; et al. (2009). "Attempt to produce element 120 in the ²⁴⁴Pu ⁵⁸Fe reaction". Phys. Rev. C. 79: 024603. doi:10.1103/PhysRevC.73.014612. {{cite journal}}: Explicit use of et al. in: |author= (help)
↑ see Flerov lab annual reports 2000-2004
↑ Natowitz, Joseph (2008). "How stable are the heaviest nuclei?". Physics. 1: 12. doi:10.1103/Physics.1.12.
↑ Morjean, M.; et al. (2008). "Fission Time Measurements: A New Probe into Superheavy Element Stability". Phys. Rev. Lett. 101: 072701. doi:10.1103/PhysRevLett.101.072701. {{cite journal}}: Explicit use of et al. in: |author= (help)
↑ GSI Proposal EAWeb (see U248)
↑ see slide 11 in Future Plan of the Experimental Program on Synthesizing the Heaviest Element at RIKEN Archived 2015-04-03 at the Wayback Machine.
↑ P. Roy Chowdhury, C. Samanta, and D. N. Basu (2006). "α decay half-lives of new superheavy elements". Phys. Rev. C. 73: 014612. doi:10.1103/PhysRevC.73.014612.{{cite journal}}: CS1 maint: multiple names: authors list (link)
↑ 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.
↑ P. Roy Chowdhury, C. Samanta, and D. N. Basu (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Phys. Rev. C. 77: 044603. doi:10.1103/PhysRevC.77.044603.{{cite journal}}: CS1 maint: multiple names: authors list (link)
↑ P. Roy Chowdhury, C. Samanta, and D. N. Basu (2008). "Nuclear half-lives for α-radioactivity of elements with 100 ≤ Z ≤ 130". At. Data & Nucl. Data Tables. 94: 781–806. doi:10.1016/j.adt.2008.01.003.{{cite journal}}: CS1 maint: multiple names: authors list (link)
↑ ^15.0 ^15.1 Feng, Zhao-Qing (2007). "Formation of superheavy nuclei in cold fusion reactions". Physical Review C. 76: 044606. doi:10.1103/PhysRevC.76.044606.
↑ ^16.0 ^16.1 ^16.2 ^16.3 ^16.4 ^16.5 Zagebraev, V; Greiner, W (2008). "Synthesis of superheavy nuclei: A search for new production reactions". Physical Review C. 78: 034610. doi:10.1103/PhysRevC.78.034610.{{cite journal}}: CS1 maint: multiple names: authors list (link)
↑ ^17.0 ^17.1 Feng, Z (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A. 816: 33. doi:10.1016/j.nuclphysa.2008.11.003.
↑ ^18.0 ^18.1 ^18.2 Nasirov, A. K. (2009). "Quasifission and fusion-fission in reactions with massive nuclei: Comparison of reactions leading to the Z=120 element". Physical Review C. 79: 024606. doi:10.1103/PhysRevC.79.024606.