Editing Unbinilium (section)

==Predicted properties==

===Nuclear stability and isotopes===
[[File:Island of Stability derived from Zagrebaev.svg|thumb|upright=2.5|alt=A 2D graph with rectangular cells colored in black-and-white colors, spanning from the llc to the urc, with cells mostly becoming lighter closer to the latter|A chart of nuclide stability as used by the Dubna team in 2010. Characterized isotopes are shown with borders. Beyond element 118 (oganesson, the last known element), the line of known nuclides is expected to rapidly enter a region of instability. The elliptical region encloses the predicted location of the island of stability.{{sfn|Zagrebaev|Karpov|Greiner|2013}}]]

[[File:Next proton shell.svg|class=skin-invert-image|thumb|upright=1.2|Orbitals with high [[azimuthal quantum number]] are raised in energy, eliminating what would otherwise be a gap in orbital energy corresponding to a closed proton shell at element 114, as shown in the left diagram which does not take this effect into account. This raises the next proton shell to the region around element 120, as shown in the right diagram, potentially increasing the half-lives of element 119 and 120 isotopes.<ref name="Kratz">{{cite conference |last1=Kratz |first1=J. V. |date=5 September 2011 |title=The Impact of Superheavy Elements on the Chemical and Physical Sciences |url=http://tan11.jinr.ru/pdf/06_Sep/S_1/02_Kratz.pdf |conference=4th International Conference on the Chemistry and Physics of the Transactinide Elements |access-date=27 August 2013}}</ref>]]
The stability of nuclei decreases greatly with the increase in atomic number after [[curium]], element 96, whose half-life is four orders of magnitude longer than that of any currently known higher-numbered element. All isotopes with an atomic number above [[mendelevium|101]] undergo [[radioactive decay]] with half-lives of less than 30 hours. No elements with atomic numbers above 82 (after [[lead]]) have stable isotopes.<ref>{{cite journal |last1=de Marcillac |first1=Pierre |last2=Coron |first2=Noël |last3=Dambier |first3=Gérard |last4=Leblanc |first4=Jacques |last5=Moalic |first5=Jean-Pierre |display-authors=3 |date=2003 |title=Experimental detection of α-particles from the radioactive decay of natural bismuth |journal=Nature |volume=422 |pages=876–878 |pmid=12712201 |doi=10.1038/nature01541 |issue=6934 |bibcode=2003Natur.422..876D |s2cid=4415582 }}</ref> Nevertheless, because of reasons not yet well understood, there is a slight increase of nuclear stability around atomic numbers [[darmstadtium|110]]–[[flerovium|114]], which leads to the appearance of what is known in nuclear physics as the "[[island of stability]]". This concept, proposed by [[University of California, Berkeley|University of California]] professor [[Glenn Seaborg]], explains why superheavy elements last longer than predicted.<ref>{{cite book |title=Van Nostrand's scientific encyclopedia |first1=Glenn D. |last1=Considine |first2=Peter H. |last2=Kulik |publisher=Wiley-Interscience |date=2002 |edition=9th |isbn=978-0-471-33230-5 |oclc=223349096 }}</ref>

Isotopes of unbinilium are predicted to have alpha decay half-lives of the order of [[microsecond]]s.<ref name="prc08ADNDT08">{{cite journal|journal=Physical Review C|volume=77|page=044603|year=2008|title=Search for long lived heaviest nuclei beyond the valley of stability|author=Chowdhury, P. Roy|author2=Samanta, C.|author3=Basu, D. N.|name-list-style=amp |doi=10.1103/PhysRevC.77.044603|bibcode=2008PhRvC..77d4603C |issue=4|arxiv=0802.3837|s2cid=119207807}}</ref><ref name="sciencedirect1">{{cite journal |author=Chowdhury |first=P. Roy |author2=Samanta |first2=C. |author3=Basu |first3=D. N. |name-list-style=amp |year=2008 |title=Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130 |journal=[[Atomic Data and Nuclear Data Tables]] |volume=94 |issue=6 |pages=781–806 |arxiv=0802.4161 |bibcode=2008ADNDT..94..781C |doi=10.1016/j.adt.2008.01.003 |s2cid=96718440}}</ref> In a [[quantum tunneling]] model with mass estimates from a macroscopic-microscopic model, the [[alpha decay|alpha-decay]] half-lives of several unbinilium [[isotope]]s (<sup>292–304</sup>Ubn) have been predicted to be around 1–20 microseconds.<ref name="prc08ADNDT08" /><ref name="half-lifesall">{{cite journal|journal=Phys. Rev. C|volume=73 |issue=1|at=014612|date=2006|title=α decay half-lives of new superheavy elements|author=Chowdhury, P. Roy |author2=Samanta, C.|author3=Basu, D. N.|name-list-style=amp |doi=10.1103/PhysRevC.73.014612 |bibcode=2006PhRvC..73a4612C |arxiv=nucl-th/0507054|s2cid=118739116 }}</ref><ref>{{cite journal| journal=Nucl. Phys. A |volume=789|issue=1–4|pages=142–154|date=2007| title=Predictions of alpha decay half lives of heavy and superheavy elements |author=Samanta, C.|author2=Chowdhury, P. Roy|author3=Basu, D.N.|name-list-style=amp |doi=10.1016/j.nuclphysa.2007.04.001|bibcode=2007NuPhA.789..142S |arxiv=nucl-th/0703086|s2cid=7496348}}</ref><ref name="sciencedirect1"/> Some heavier isotopes may be more stable; Fricke and Waber predicted <sup>320</sup>Ubn to be the most stable unbinilium isotope in 1971.<ref name="Fricke1971" /> Since unbinilium is expected to decay via a cascade of alpha decays leading to [[spontaneous fission]] around [[copernicium]], the total half-lives of unbinilium isotopes are also predicted to be measured in microseconds.<ref name="Haire" /><ref name="Hofmann" /> This has consequences for the synthesis of unbinilium, as isotopes with half-lives below one microsecond would decay before reaching the detector.<ref name="Haire" /><ref name="Hofmann" /> Nevertheless, new theoretical models show that the expected gap in energy between the [[nuclear shell model|proton orbitals]] 2f<sub>7/2</sub> (filled at element 114) and 2f<sub>5/2</sub> (filled at element 120) is smaller than expected, so that element 114 no longer appears to be a stable spherical closed nuclear shell, and this energy gap may increase the stability of elements 119 and 120. The next [[doubly magic]] nucleus is now expected to be around the spherical <sup>306</sup>Ubb (element 122), but the expected low half-life and low production [[cross section (physics)|cross section]] of this nuclide makes its synthesis challenging.<ref name="Kratz" />

Given that element 120 fills the 2f<sub>5/2</sub> proton orbital, much attention has been given to the compound nucleus <sup>302</sup>Ubn* and its properties. Several experiments have been performed between 2000 and 2008 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus <sup>302</sup>Ubn*. Two nuclear reactions have been used, namely <sup>244</sup>Pu+<sup>58</sup>Fe and <sup>238</sup>U+<sup>64</sup>Ni. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as <sup>132</sup>[[tin|Sn]] (''[[atomic number|Z]]''&nbsp;=&nbsp;50, ''[[neutron number|N]]''&nbsp;=&nbsp;82). It was also found that the yield for the fusion-fission pathway was similar between <sup>48</sup>Ca and <sup>58</sup>Fe projectiles, suggesting a possible future use of <sup>58</sup>Fe projectiles in superheavy element formation.<ref>{{cite web |url=http://www1.jinr.ru/Reports/Reports_eng_arh.html |title=JINR Publishing Department: Annual Reports (Archive) |author=JINR |date=1998–2014 |website=jinr.ru |publisher=JINR |access-date=23 September 2016}}</ref>

In 2008, the team at [[Grand Accélérateur National d'Ions Lourds|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''&nbsp;=&nbsp;114, 120, 124, or 126). The team studied the nuclear fusion reaction between uranium ions and a target of natural nickel:<ref name="Natowitz" /><ref name="Morjean" />

:{{nuclide|U|238}} + {{nuclide|Ni|nat}} → {{nuclide|Ubn|296,298,299,300,302}}* → fission

The results indicated that nuclei of unbinilium were produced at high (≈70&nbsp;MeV) excitation energy which underwent fission with measurable half-lives just over 10<sup>−18</sup> s.<ref name="Natowitz" /><ref name="Morjean" /> Although very short (indeed insufficient for the element to be considered by [[IUPAC]] to exist, because a compound nucleus has no internal structure and its nucleons have not been arranged into shells until it has survived for 10<sup>−14</sup>&nbsp;s, when it forms an electronic cloud),<ref>{{cite web |title=Kernchemie |url=http://www.kernchemie.de/Transactinides/Transactinide-2/transactinide-2.html |access-date=23 September 2016|language=de|trans-title=Nuclear Chemistry}}</ref> the ability to measure such a process indicates a strong shell effect at ''Z''&nbsp;=&nbsp;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 <sup>294</sup>Og measured in experiments at Dubna. Similar experiments have indicated a similar phenomenon at [[unbiquadium|element 124]] but not for [[flerovium]], suggesting that the next proton shell does in fact lie beyond element 120.<ref name="Natowitz">{{cite journal |doi=10.1103/Physics.1.12|title=How stable are the heaviest nuclei?|date=2008|author=Natowitz, Joseph |journal=Physics|volume=1|pages=12|bibcode = 2008PhyOJ...1...12N |doi-access=}}</ref><ref name="Morjean">{{cite journal|journal=Phys. Rev. Lett. |volume=101|issue=7|date=2008 |at=072701|title=Fission Time Measurements: A New Probe into Superheavy Element Stability|doi=10.1103/PhysRevLett.101.072701|pmid=18764526|bibcode=2008PhRvL.101g2701M |last1=Morjean|first1=M.|last2=Jacquet|first2=D. |last3=Charvet |first3=J. |display-authors=etal |url=http://hal.in2p3.fr/in2p3-00289928/document}}</ref> In September 2007, the team at RIKEN began a program utilizing <sup>248</sup>Cm targets and have indicated future experiments to probe the possibility of 120 being the next proton magic number (and 184 being the next neutron magic number) using the aforementioned nuclear reactions to form <sup>302</sup>Ubn*, as well as <sup>248</sup>Cm+<sup>54</sup>Cr. They also planned to further chart the region by investigating the nearby compound nuclei <sup>296</sup>Og*, <sup>298</sup>Og*, <sup>306</sup>Ubb*, and <sup>308</sup>Ubb*.<ref>{{cite web |title=Future Plan of the Experimental Program on Synthesizing the Heaviest Element at RIKEN |last1=Morita |first1=K. |date=28 September 2007 |url=http://www-win.gsi.de/tasca07/contributions/TASCA07_Contribution_Morita.pdf |access-date=23 September 2016 |url-status=dead |archive-url=https://web.archive.org/web/20150403120113/http://www-win.gsi.de/tasca07/contributions/TASCA07_Contribution_Morita.pdf |archive-date=3 April 2015 }}</ref>

The most likely isotopes of unbinilium to be synthesised in the near future are <sup>295</sup>Ubn through <sup>299</sup>Ubn, because they can be produced in the 3n and 4n channels of the <sup>249–251</sup>Cf+<sup>50</sup>Ti, <sup>245</sup>Cm+<sup>54</sup>Cr, and <sup>248</sup>Cm+<sup>54</sup>Cr reactions.<ref name=jinr2024>{{Cite web |url=https://indico.jinr.ru/event/4343/contributions/28663/attachments/20748/36083/U%20+%20Cr%20AYSS%202024.pptx |title=Synthesis and study of the decay properties of isotopes of superheavy element Lv in Reactions <sup>238</sup>U + <sup>54</sup>Cr and <sup>242</sup>Pu + <sup>50</sup>Ti |last=Ibadullayev |first=Dastan |date=2024 |website=jinr.ru |publisher=[[Joint Institute for Nuclear Research]] |access-date=2 November 2024 |quote=}}</ref>

===Atomic and physical===
Being the second [[period 8 element]], unbinilium is predicted to be an alkaline earth metal, below [[beryllium]], [[magnesium]], [[calcium]], [[strontium]], [[barium]], and [[radium]]. Each of these elements has two [[valence electron]]s in the outermost s-orbital (valence electron configuration ''n''s<sup>2</sup>), which is easily lost in chemical reactions to form the +2 [[oxidation state]]: thus the alkaline earth metals are rather [[reactivity (chemistry)|reactive]] elements, with the exception of beryllium due to its small size. Unbinilium is predicted to continue the trend and have a valence electron configuration of 8s<sup>2</sup>. It is therefore expected to behave much like its lighter [[Congener (chemistry)|congeners]]; however, it is also predicted to differ from the lighter alkaline earth metals in some properties.<ref name="Haire" />

The main reason for the predicted differences between unbinilium and the other alkaline earth metals is the [[spin–orbit interaction|spin–orbit (SO) interaction]]—the mutual interaction between the electrons' motion and [[Spin (physics)|spin]]. The SO interaction is especially strong for the superheavy elements because their electrons move faster—at velocities comparable to the [[speed of light]]—than those in lighter atoms.<ref name="Thayer" /> In unbinilium atoms, it lowers the 7p and 8s electron energy levels,<!-- |level is an important word. Lv has no 8s electrons but they've been shown to affect its chemistry--> stabilizing the corresponding electrons, but two of the 7p electron energy levels are more stabilized than the other four.<ref name="Faegri">{{Cite journal | last1 = Fægri Jr. | first1 = Knut | last2 = Saue | first2 = Trond | doi = 10.1063/1.1385366 | title = Diatomic molecules between very heavy elements of group 13 and group 17: A study of relativistic effects on bonding | journal = The Journal of Chemical Physics | volume = 115 | issue = 6 | pages = 2456 | year = 2001 | publisher = American Institute of Physics |bibcode = 2001JChPh.115.2456F | doi-access = free }}</ref> The effect is called subshell splitting, as it splits the 7p subshell into more-stabilized and the less-stabilized parts. Computational chemists understand the split as a change of the second ([[azimuthal quantum number|azimuthal]]) [[quantum number]] ''l'' from 1 to 1/2 and 3/2 for the more-stabilized and less-stabilized parts of the 7p subshell, respectively.<ref name="Thayer" />{{efn|The quantum number corresponds to the letter in the electron orbital name: 0 to s, 1 to p, 2 to d, etc. See [[azimuthal quantum number]] for more information.}} Thus, the outer 8s electrons of unbinilium are stabilized and become harder to remove than expected, while the 7p<sub>3/2</sub> electrons are correspondingly destabilized, perhaps allowing them to participate in chemical reactions.<ref name="Haire" /> This stabilization of the outermost s-orbital (already significant in radium) is the key factor affecting unbinilium's chemistry, and causes all the trends for atomic and molecular properties of alkaline earth metals to reverse direction after barium.<ref name="Pershina">{{cite book |last=Pershina |first=Valeria |editor1-last=Schädel |editor1-first=Matthias |editor2-last=Shaughnessy |editor2-first=Dawn |chapter=Theoretical Chemistry of the Heaviest Elements |date=2014 |edition=2nd |title=The Chemistry of Superheavy Elements |publisher=Springer-Verlag |pages=204–7 |isbn=978-3-642-37465-4 |doi=10.1007/978-3-642-37466-1|s2cid=122675117 |chapter-url=https://cds.cern.ch/record/643991 }}</ref>

{| align="center"
|-
| valign=bottom | [[File:Atomic radius of alkali metals and alkaline earth metals.svg|class=skin-invert-image|thumb|none|upright=1.2|[[Empirical]] (Na–Cs, Mg–Ra) and predicted (Fr–Uhp, Ubn–Uhh) atomic radii of the alkali and alkaline earth metals from the [[period 3 element|third]] to the [[period 9 element|ninth period]], measured in [[angstrom]]s<ref name="Haire" /><ref name="pyykko" />]]
| [[File:Ionization energy of alkali metals and alkaline earth metals.svg|class=skin-invert-image|thumb|none|upright=1|Empirical (Na–Fr, Mg–Ra) and predicted (Uue–Uhp, Ubn–Uhh) ionization energy of the alkali and alkaline earth metals from the third to the ninth period, measured in electron volts<ref name="Haire" /><ref name="pyykko">{{Cite journal|last1=Pyykkö|first1=Pekka|title=A suggested periodic table up to Z ≤ 172, based on Dirac–Fock calculations on atoms and ions|journal=Physical Chemistry Chemical Physics|volume=13|issue=1|pages=161–8|date=2011|pmid=20967377|doi=10.1039/c0cp01575j|bibcode = 2011PCCP...13..161P }}</ref>]]
|}

Due to the stabilization of its outer 8s electrons, unbinilium's first [[ionization energy]]—the energy required to remove an electron from a neutral atom—is predicted to be 6.0&nbsp;eV, comparable to that of calcium.<ref name="Haire" /> The electron of the [[hydrogen-like atom|hydrogen-like]] unbinilium atom—oxidized so it has only one electron, Ubn<sup>119+</sup>—is predicted to move so quickly that its mass is 2.05 times that of a non-moving electron, a feature coming from the [[Relativistic quantum chemistry|relativistic effects]]. For comparison, the figure for hydrogen-like radium is 1.30 and the figure for hydrogen-like barium is 1.095.<ref name="Thayer" /> According to simple extrapolations of relativity laws, that indirectly indicates the contraction of the [[atomic radius]]<ref name="Thayer" /> to around 200&nbsp;[[picometer|pm]],<ref name="Haire" /> very close to that of strontium (215&nbsp;pm); the [[ionic radius]] of the Ubn<sup>2+</sup> ion is also correspondingly lowered to 160&nbsp;pm.<ref name="Haire" /> The trend in electron affinity is also expected to reverse direction similarly at radium and unbinilium.<ref name="Pershina" />

Unbinilium should be a [[solid]] at room temperature, with melting point 680&nbsp;°C:<ref name="BFricke">{{cite journal |last1=Fricke |first1=Burkhard |year=1975 |title=Superheavy elements: a prediction of their chemical and physical properties |journal=Recent Impact of Physics on Inorganic Chemistry |volume=21 |pages=[https://archive.org/details/recentimpactofph0000unse/page/89 89–144] |doi=10.1007/BFb0116498 |url=https://archive.org/details/recentimpactofph0000unse/page/89 |access-date=4 October 2013 |series=Structure and Bonding |isbn=978-3-540-07109-9 }}</ref> this continues the downward trend down the group, being lower than the value 700&nbsp;°C for radium.<ref>{{RubberBible86th}}</ref> The boiling point of unbinilium is expected to be around 1700&nbsp;°C, which is lower than that of all the previous elements in the group (in particular, radium boils at 1737&nbsp;°C), following the downward periodic trend.<ref name="Fricke1971" /> The density of unbinilium has been predicted to be 7&nbsp;g/cm<sup>3</sup>, continuing the trend of increasing density down the group: the value for radium is 5.5&nbsp;g/cm<sup>3</sup>.<ref name="Fricke1971" /><ref name="B&K" />

===Chemical===
{| class="wikitable floatright" style="font-size:85%;"
|+ Bond lengths and bond-dissociation energies of alkaline earth metal dimers. Data for Ba<sub>2</sub>, Ra<sub>2</sub> and Ubn<sub>2</sub> is predicted.<ref name="Pershina" />
! Compound
! Bond length<br />(Å)
! Bond-dissociation<br />energy (eV)
|-
! Ca<sub>2</sub>
| 4.277
| 0.14
|-
! Sr<sub>2</sub>
| 4.498
| 0.13
|-
! Ba<sub>2</sub>
| 4.831
| 0.23
|-
! Ra<sub>2</sub>
| 5.19
| 0.11
|-
! Ubn<sub>2</sub>
| 5.65
| 0.02
|}
The chemistry of unbinilium is predicted to be similar to that of the alkaline earth metals,<ref name="Haire" /> but it would probably behave more like calcium or strontium<ref name="Haire" /> than barium or radium. Like strontium, unbinilium should react vigorously with air to form an oxide (UbnO) and with water to form the hydroxide (Ubn(OH)<sub>2</sub>), which would be a strong [[base (chemistry)|base]], and releasing [[hydrogen]] gas. It should also react with the [[halogen]]s to form salts such as UbnCl<sub>2</sub>.<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7|page=586}}</ref> While these reactions would be expected from [[periodic trends]], their lowered intensity is somewhat unusual, as ignoring relativistic effects, periodic trends would predict unbinilium to be even more reactive than barium or radium. This lowered [[reactivity (chemistry)|reactivity]] is due to the relativistic stabilization of unbinilium's valence electron, increasing unbinilium's first ionization energy and decreasing the [[metallic radius|metallic]] and [[ionic radius|ionic radii]];<ref name="EB">{{cite encyclopedia|author=Seaborg|url=http://www.britannica.com/EBchecked/topic/603220/transuranium-element|title=transuranium element (chemical element)|encyclopedia=Encyclopædia Britannica|date=c. 2006|access-date=2010-03-16}}</ref> this effect is already seen for radium.<ref name="Haire" /> On the other hand, the ionic radius of the Ubn<sup>2+</sup> ion is predicted to be larger than that of Sr<sup>2+</sup>, because the 7p orbitals are destabilized and are thus larger than the p-orbitals of the lower shells.<ref name=Thayer/>

Unbinilium may also show the +4 [[oxidation state]],<ref name="Haire" /> which is not seen in any other alkaline earth metal,<ref name="Greenwood&Earnshaw">{{Greenwood&Earnshaw|p=28}}</ref> in addition to the +2 oxidation state that is characteristic of the other alkaline earth metals and is also the main oxidation state of all the known alkaline earth metals: this is because of the destabilization and expansion of the 7p<sub>3/2</sub> spinor, causing its outermost electrons to have a lower ionization energy than what would otherwise be expected.<ref name="Haire" /><ref name="Greenwood&Earnshaw" /> The +6 state involving all the 7p<sub>3/2</sub> electrons has been suggested in a [[hexafluoride]], UbnF<sub>6</sub>.<ref name=Cao/> The +1 state may also be isolable.<ref name="Thayer" /> Many unbinilium compounds are expected to have a large [[covalent]] character, due to the involvement of the 7p<sub>3/2</sub> electrons in the bonding: this effect is also seen to a lesser extent in radium, which shows some 6s and 6p<sub>3/2</sub> contribution to the bonding in [[radium fluoride]] (RaF<sub>2</sub>) and astatide (RaAt<sub>2</sub>), resulting in these compounds having more covalent character.<ref name="Thayer" /> The [[standard reduction potential]] of the Ubn<sup>2+</sup>/Ubn couple is predicted to be −2.9&nbsp;V, which is almost exactly the same as that for the Sr<sup>2+</sup>/Sr couple of strontium (&minus;2.899&nbsp;V).<ref name="BFricke" />

{| class="wikitable floatright" style="font-size:85%;"
|+ Bond lengths and bond-dissociation energies of MAu (M = an alkaline earth metal). All data is predicted, except for CaAu.<ref name="Pershina" />
! Compound
! Bond length<br />(Å)
! Bond-dissociation<br />energy (kJ/mol)
|-
! CaAu
| 2.67
| 2.55
|-
! SrAu
| 2.808
| 2.63
|-
! BaAu
| 2.869
| 3.01
|-
! RaAu
| 2.995
| 2.56
|-
! UbnAu
| 3.050
| 1.90
|}
In the gas phase, the alkaline earth metals do not usually form covalently bonded diatomic molecules like the alkali metals do, since such molecules would have the same number of electrons in the bonding and antibonding orbitals and would have very low [[dissociation energy|dissociation energies]].<ref name="Be2">{{cite book |last1=Keeler |first1=James |last2=Wothers |first2=Peter |date=2003 |title=Why Chemical Reactions Happen |publisher=[[Oxford University Press]] |page=74 |isbn=978-0-19-924973-2}}</ref> Thus, the M–M bonding in these molecules is predominantly through [[van der Waals force]]s.<ref name="Pershina" /> The metal–metal [[bond length]]s in these M<sub>2</sub> molecules increase down the group from Ca<sub>2</sub> to Ubn<sub>2</sub>. On the other hand, their metal–metal [[bond-dissociation energy|bond-dissociation energies]] generally increase from Ca<sub>2</sub> to Ba<sub>2</sub> and then drop to Ubn<sub>2</sub>, which should be the most weakly bound of all the group 2 homodiatomic molecules. The cause of this trend is the increasing participation of the p<sub>3/2</sub> and d electrons as well as the relativistically contracted s orbital.<ref name="Pershina" /> From these M<sub>2</sub> dissociation energies, the [[enthalpy of sublimation]] (Δ''H''<sub>sub</sub>) of unbinilium is predicted to be 150&nbsp;kJ/mol.<ref name="Pershina" />

{| class="wikitable floatright" style="font-size:85%;"
|+Bond lengths, harmonic frequency, vibrational anharmonicity and bond-dissociation energies of MH and MAu (M = an alkaline earth metal). Data for UbnH and UbnAu are predicted.<ref name=":0">{{Cite journal|last1=Skripnikov|first1=L.V.|last2=Mosyagin|first2=N.S.|last3=Titov|first3=A.V.|date=January 2013|title=Relativistic coupled-cluster calculations of spectroscopic and chemical properties for element 120|journal=Chemical Physics Letters|volume=555|pages=79–83|doi=10.1016/j.cplett.2012.11.013|arxiv=1202.3527|bibcode=2013CPL...555...79S |s2cid=96581438}}</ref> Data for BaH is taken from experiment,<ref>{{Cite journal|last1=Knight|first1=L. B.|last2=Easley|first2=W. C.|last3=Weltner|first3=W.|last4=Wilson|first4=M.|date=January 1971|title=Hyperfine Interaction and Chemical Bonding in MgF, CaF, SrF, and BaF molecules|journal=The Journal of Chemical Physics|volume=54|issue=1|pages=322–329|doi=10.1063/1.1674610|bibcode=1971JChPh..54..322K |issn=0021-9606}}</ref> except bond-dissociation energy.<ref name=":0" /> Data for BaAu is taken from experiment,<ref>{{Cite book|title=Constants of Diatomic Molecules|publisher=Van Nostrand-Reinhold|year=1979|location=New York}}</ref> except bond-dissociation energy and bond length.<ref name=":0" />
!Compound
!Bond length<br />(Å)
!Harmonic<br />frequency,<br />cm<sup>−1</sup>
!Vibrational<br />anharmonicity,<br />cm<sup>−1</sup>
!Bond-dissociation<br />energy (eV)
|-
|'''UbnH'''
|2.38
|1070
|20.1
|1.00
|-
|'''BaH'''
|2.23
|1168
|14.5
|2.06
|-
|
|
|
|
|
|-
|'''UbnAu'''
|3.03
| 100
| 0.13
|1.80
|-
|'''BaAu'''
|2.91 
| 129
| 0.18
|2.84
|}
The Ubn–[[gold|Au]] bond should be the weakest of all bonds between gold and an alkaline earth metal, but should still be stable. This gives extrapolated medium-sized adsorption enthalpies (−Δ''H''<sub>ads</sub>) of 172&nbsp;kJ/mol on gold (the radium value should be 237&nbsp;kJ/mol) and 50&nbsp;kJ/mol on [[silver]], the smallest of all the alkaline earth metals, that demonstrate that it would be feasible to study the [[chromatography|chromatographic]] [[adsorption]] of unbinilium onto surfaces made of [[noble metal]]s.<ref name="Pershina" /> The Δ''H''<sub>sub</sub> and −Δ''H''<sub>ads</sub> values are correlated for the alkaline earth metals.<ref name="Pershina" />