Editing Ununennium (section)

===Atomic and physical===
Being the first [[period 8 element]], ununennium is predicted to be an alkali metal, taking its place in the periodic table below [[lithium]], [[sodium]], [[potassium]], [[rubidium]], [[caesium]], and [[francium]]. Each of these elements has one [[valence electron]] in the outermost s-orbital (valence electron configuration ''n''s<sup>1</sup>), which is easily lost in chemical reactions to form the +1 [[oxidation state]]: thus, the alkali metals are very [[reactivity (chemistry)|reactive]] elements. Ununennium is predicted to continue the trend and have a valence electron configuration of 8s<sup>1</sup>. It is therefore expected to behave much like its lighter [[Congener (chemistry)|congener]]s; however, it is also predicted to differ from the lighter alkali metals in some properties.<ref name="Haire" />

The main reason for the predicted differences between ununennium and the other alkali 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 speeds comparable to the [[speed of light]]—than those in lighter atoms.<ref name="Thayer" /> In ununennium 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 |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 {{frac|1|2}} and {{frac|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 electron of ununennium is stabilized and becomes 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 francium) is the key factor affecting ununennium's chemistry, and causes all the trends for atomic and molecular properties of alkali metals to reverse direction after caesium.<ref name="Pershina" />

{| 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" />]]
| valign=bottom | [[File:Electron affinity of alkali metals.svg|class=skin-invert-image|thumb|none|upright=1.2|Empirical (Na–Cs), semi-empirical (Fr), and predicted (Uue) electron affinities of the alkali metals from the third to the [[period 8 element|eighth period]], measured in [[electron volt]]s.<ref name="Haire" /><ref name="pyykko" /> They decrease from Li to Cs, but the Fr value, {{val|492|10|u=meV}}, is 20&nbsp;meV higher than that of Cs, and that of Uue is much higher still at 662&nbsp;meV.<ref name="Landau">{{cite journal |last1=Landau |first1=Arie |last2=Eliav |first2=Ephraim |first3=Yasuyuki |last3=Ishikawa |first4=Uzi |last4=Kador |date=25 May 2001 |title=Benchmark calculations of electron affinities of the alkali atoms sodium to eka-francium (element 119) |url=https://www.researchgate.net/publication/234859102 |journal=Journal of Chemical Physics |volume=115 |issue=6 |pages=2389–2392 |doi=10.1063/1.1386413 |access-date=15 September 2015|bibcode=2001JChPh.115.2389L }}</ref>]]
| valign=bottom | [[File:Ionization energy of alkali metals and alkaline earth metals.svg|class=skin-invert-image|thumb|none |upright=1.25|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=161–168|date=2011|pmid=20967377|doi=10.1039/c0cp01575j|bibcode=2011PCCP...13..161P |s2cid=31590563 }}</ref>]]
|}

Due to the stabilization of its outer 8s electron, ununennium's first [[ionization energy]]—the energy required to remove an electron from a neutral atom—is predicted to be 4.53&nbsp;eV, higher than those of the known alkali metals from potassium onward. This effect is so large that unbiunium (element 121) is predicted to have a lower ionization energy of 4.45&nbsp;eV, so that the alkali metal in period 8 would not have the lowest ionization energy in the period, as is true for all previous periods.<ref name="Haire" /> Ununennium's [[electron affinity]] is expected to be far greater than that of caesium and francium; indeed, ununennium is expected to have an electron affinity higher than all the alkali metals lighter than it at about 0.662&nbsp;eV, close to that of [[cobalt]] (0.662&nbsp;eV) and [[chromium]] (0.676&nbsp;eV).<ref name="Landau" /> Relativistic effects also cause a very large drop in the [[polarizability]] of ununennium<ref name="Haire" /> to 169.7&nbsp;[[atomic unit|a.u.]]<ref name="Borschevsky">{{cite journal |last1=Borschevsky |first1=A. |last2=Pershina |first2=V. |last3=Eliav |first3=E. |last4=Kaldor |first4=U. |date=22 March 2013 |title=''Ab initio'' studies of atomic properties and experimental behavior of element 119 and its lighter homologs |journal=The Journal of Chemical Physics |volume=138 |issue=12 |at=124302 |doi=10.1063/1.4795433 |pmid=23556718 |bibcode=2013JChPh.138l4302B |url=http://repository.gsi.de/record/52121/files/PHN-ENNA-THEORY-08.pdf |access-date=5 December 2018 |archive-date=15 March 2022 |archive-url=https://web.archive.org/web/20220315200718/https://repository.gsi.de/record/52121/files/PHN-ENNA-THEORY-08.pdf |url-status=live }}</ref> Indeed, the static dipole polarisability (α<sub>''D''</sub>) of ununennium, a quantity for which the impacts of relativity are proportional to the square of the element's atomic number, has been calculated to be small and similar to that of sodium.<ref>{{cite journal |display-authors=3 |last1=Lim |first1=Ivan S. |last2=Pernpointner |first2=Markus |first3=Michael |last3=Seth |first4=Jon K. |last4=Laerdahl |first5=Peter |last5=Schwerdtfeger |first6=Pavel |last6=Neogrady |first7=Miroslav |last7=Urban |date=1999 |title=Relativistic coupled-cluster static dipole polarizabilities of the alkali metals from Li to element 119 |journal=Physical Review A |volume=60 |issue=4 |at=2822 |doi=10.1103/PhysRevA.60.2822 |bibcode=1999PhRvA..60.2822L}}</ref>

The electron of the [[hydrogen-like atom|hydrogen-like]] ununennium atom—oxidized so it has only one electron, Uue<sup>118+</sup>—is predicted to move so quickly that its mass is 1.99 times that of a non-moving electron, a consequence of [[Relativistic quantum chemistry|relativistic effects]]. For comparison, the figure for hydrogen-like francium is 1.29 and the figure for hydrogen-like caesium is 1.091.<ref name="Thayer" /> According to simple extrapolations of relativity laws, that indirectly indicates the contraction of the [[atomic radius]]<ref name="Thayer" /> to around 240&nbsp;[[picometer|pm]],<ref name="Haire" /> very close to that of rubidium (247&nbsp;pm); the [[metallic radius]] is also correspondingly lowered to 260&nbsp;pm.<ref name="Haire" /> The [[ionic radius]] of Uue<sup>+</sup> is expected to be 180&nbsp;pm.<ref name="Haire" />

Ununennium is predicted to have a melting point between 0&nbsp;°C and 30&nbsp;°C: thus it may be a [[liquid]] at room temperature.{{Fricke1975}} It is not known whether this continues the trend of decreasing melting points down the group, as caesium's melting point is 28.5&nbsp;°C and francium's is estimated to be around 8.0&nbsp;°C.<ref name="L&P">{{cite book |title=Analytical Chemistry of Technetium, Promethium, Astatine, and Francium |first1=Avgusta Konstantinovna |last1=Lavrukhina |first2=Aleksandr Aleksandrovich |last2=Pozdnyakov |year=1970 |publisher=Ann Arbor–Humphrey Science Publishers |others=Translated by R. Kondor |isbn=978-0-250-39923-9 |page=269}}</ref> The boiling point of ununennium is expected to be around 630&nbsp;°C, similar to that of francium, estimated to be around 620&nbsp;°C; this is lower than caesium's boiling point of 671&nbsp;°C.<ref name="Fricke1971" /><ref name="L&P" /> The density of ununennium has been variously predicted to be between 3 and 4&nbsp;g/cm<sup>3</sup>, continuing the trend of increasing density down the group: the density of francium is estimated at 2.48&nbsp;g/cm<sup>3</sup>, and that of caesium is known to be 1.93&nbsp;g/cm<sup>3</sup>.<ref name="Fricke1971" /><ref name="B&K" /><ref name="L&P" />