Editing Flerovium (section)

==Predicted properties==
Very few properties of flerovium or its compounds have been measured; due to its extremely limited and expensive production<ref name="Superheavy element Bloomberg"/> and the fact that it decays very quickly. A few singular properties have been measured, but for the most part, properties of flerovium remain unknown and only predictions are available.

===Nuclear stability and isotopes===
{{main|Isotopes of flerovium}}
[[File:IBA nuclear shells.svg|thumb|right|upright=1.6|Regions of differently shaped nuclei, as predicted by the [[interacting boson model]]<ref name="Kratz" />]]
The basis of the chemical [[periodic trends|periodicity]] in the periodic table is the electron shell closure at each noble gas ([[atomic number]]s [[helium|2]], [[neon|10]], [[argon|18]], [[krypton|36]], [[xenon|54]], [[radon|86]], and [[oganesson|118]]): as any further electrons must enter a new shell with higher energy, closed-shell electron configurations are markedly more stable, hence the inertness of noble gases.<ref name="Fricke1971" /> Protons and neutrons are also known to form closed nuclear shells, so the same happens at nucleon shell closures, which happen at specific nucleon numbers often dubbed "magic numbers". The known magic numbers are 2, 8, 20, 28, 50, and 82 for protons and neutrons; also 126 for neutrons.<ref name="Fricke1971" /> Nuclei with magic proton and [[neutron number]]s, such as [[helium-4]], [[oxygen-16]], [[calcium-48]], and [[lead-208]], are "doubly magic" and are very stable. This stability is very important for [[superheavy element]]s: with no stabilization, half-lives would be expected by exponential extrapolation to be [[nanosecond]]s at [[darmstadtium]] (element 110), because the ever-increasing electrostatic repulsion between protons overcomes the limited-range [[strong nuclear force]] that holds nuclei together. The next closed nucleon shells (magic numbers) are thought to denote the centre of the long-sought island of stability, where half-lives to alpha decay and spontaneous fission lengthen again.<ref name="Fricke1971" />

[[File:Next proton shell.svg|thumb|right|upright=1.6|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. This raises the next proton shell to the region around [[unbinilium|element 120]].<ref name="Kratz" />]]
Initially, by analogy with neutron magic number 126, the next proton shell was also expected at [[unbihexium|element 126]], too far beyond the synthesis capabilities of the mid-20th century to get much theoretical attention. In 1966, new values for the potential and [[spin–orbit interaction]] in this region of the periodic table<ref>{{Cite book|last1=Kalinkin|first1=B. N.|last2=Gareev|first2=F. A.|arxiv=nucl-th/0111083v2|title=Synthesis of Superheavy elements and Theory of Atomic Nucleus|date=2001|doi=10.1142/9789812777300_0009|journal=Exotic Nuclei|pages=118|isbn=978-981-238-025-8|bibcode=2002exnu.conf..118K|citeseerx=10.1.1.264.7426|s2cid=119481840}}</ref> contradicted this and predicted that the next proton shell would instead be at element 114,<ref name="Fricke1971" /> and that nuclei in this region would be relatively stable against spontaneous fission.<ref name="Fricke1971" /> The expected closed neutron shells in this region were at neutron number 184 or 196, making <sup>298</sup>Fl and <sup>310</sup>Fl candidates for being doubly magic.<ref name="Fricke1971" /> 1972 estimates predicted a half-life of around 1&nbsp;year for <sup>298</sup>Fl, which was expected to be near an [[island of stability]] centered near <sup>294</sup>Ds (with a half-life around 10<sup>10</sup>&nbsp;years, comparable to <sup>232</sup>[[thorium|Th]]).<ref name="Fricke1971" /> After making the first isotopes of elements 112–118 at the turn of the 21st century, it was found that these neutron-deficient isotopes were stabilized against fission. In 2008 it was thus hypothesized that the stabilization against fission of these nuclides was due to their [[Spheroid|oblate]] nuclei, and that a region of oblate nuclei was centred on <sup>288</sup>Fl. Also, new theoretical models showed that the expected energy gap between the proton orbitals 2f<sub>7/2</sub> (filled at element 114) and 2f<sub>5/2</sub> (filled at [[unbinilium|element 120]]) was smaller than expected, so element 114 no longer appeared to be a stable spherical closed nuclear shell. The next doubly magic nucleus is now expected to be around <sup>306</sup>Ubb, but this nuclide's expected short half-life and low production [[cross section (physics)|cross section]] make its synthesis challenging.<ref name="Kratz" /> Still, the island of stability is expected to exist in this region, and nearer its centre (which has not been approached closely enough yet) some nuclides, such as <sup>291</sup>[[moscovium|Mc]] and its alpha- and beta-decay [[decay product|daughters]],{{efn|Specifically, <sup>291</sup>Mc, <sup>291</sup>Fl, <sup>291</sup>Nh, <sup>287</sup>Nh, <sup>287</sup>Cn, <sup>287</sup>Rg, <sup>283</sup>Rg, and <sup>283</sup>Ds, which are expected to decay to the relatively longer-lived nuclei <sup>283</sup>Mt, <sup>287</sup>Ds, and <sup>291</sup>Cn.<ref name="Zagrebaev" />}} may be found to decay by [[positron emission]] or [[electron capture]] and thus move into the centre of the island.<ref name="Zagrebaev">{{cite conference|last1=Zagrebaev|first1=Valeriy|last2=Karpov|first2=Alexander|last3=Greiner|first3=Walter|date=2013|title=Future of superheavy element research: Which nuclei could be synthesized within the next few years?|publisher=IOP Science|book-title=Journal of Physics: Conference Series|volume=420|pages=1–15|url=http://iopscience.iop.org/1742-6596/420/1/012001/pdf/1742-6596_420_1_012001.pdf|access-date=20 August 2013}}</ref> Due to the expected high fission barriers, any nucleus in this island of stability would decay exclusively by alpha decay and perhaps some electron capture and [[beta decay]],<ref name="Fricke1971" /> both of which would bring the nuclei closer to the beta-stability line where the island is expected to be. Electron capture is needed to reach the island, which is problematic because it is not certain that electron capture is a major decay mode in this region of the [[chart of nuclides]].<ref name="Zagrebaev" />

Experiments were done in 2000–2004 at Flerov Laboratory of Nuclear Reactions in Dubna studying the fission properties of the compound nucleus <sup>292</sup>Fl by bombarding <sup>244</sup>Pu with accelerated <sup>48</sup>Ca ions.<ref name="jinr20006" /> A compound nucleus is a loose combination of [[nucleon]]s that have not yet arranged themselves into nuclear shells. It has no internal structure and is held together only by the collision forces between the two nuclei.<ref name="compoundnucleus" />{{efn|It is estimated that it requires around 10<sup>−14</sup>&nbsp;s for the nucleons to arrange themselves into nuclear shells, at which point the compound nucleus becomes a [[nuclide]], and this number is used by IUPAC as the minimum half-life a claimed isotope must have to be recognized as a nuclide.<ref name="compoundnucleus">{{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=590}}</ref>}} Results showed how such nuclei fission mainly by expelling doubly magic or nearly doubly magic fragments such as <sup>40</sup>[[calcium|Ca]], <sup>132</sup>[[tin|Sn]], <sup>208</sup>[[lead|Pb]], or <sup>209</sup>[[bismuth|Bi]]. It was also found that <sup>48</sup>Ca and <sup>58</sup>[[iron|Fe]] projectiles had a similar yield for the fusion-fission pathway, suggesting possible future use of <sup>58</sup>Fe projectiles in making superheavy elements.<ref name="jinr20006">
{{cite web
|title=JINR Annual Reports 2000–2006
|url=http://www1.jinr.ru/Reports/Reports_eng_arh.html
|publisher=[[Joint Institute for Nuclear Research|JINR]]
|access-date=27 August 2013
}}</ref> It has also been suggested that a neutron-rich flerovium isotope can be formed by quasifission (partial fusion followed by fission) of a massive nucleus.<ref name="ZG" /> Recently it has been shown that multi-nucleon transfer reactions in collisions of actinide nuclei (such as [[uranium]] and [[curium]]) might be used to make neutron-rich superheavy nuclei in the island of stability,<ref name="ZG">
{{cite journal
|last1=Zagrebaev|first1=V.
|last2=Greiner|first2=W.
|year=2008
|title=Synthesis of superheavy nuclei: A search for new production reactions
|journal=[[Physical Review C]]
|volume=78|issue=3|page=034610
|arxiv=0807.2537
|bibcode=2008PhRvC..78c4610Z
|doi=10.1103/PhysRevC.78.034610
}}</ref> though production of neutron-rich [[nobelium]] or [[seaborgium]] is more likely.<ref name="Zagrebaev" />

Theoretical estimates of alpha decay half-lives of flerovium isotopes, support the experimental data.<ref name="half-lifes">
{{cite journal
|last1=Chowdhury|first1=P. R.
|last2=Samanta|first2=C.
|last3=Basu|first3=D. N.
|date=2006
|title=α decay half-lives of new superheavy elements
|journal=[[Physical Review C]]
|volume=73|issue=1|page=014612
|arxiv=nucl-th/0507054
|bibcode=2006PhRvC..73a4612C
|doi=10.1103/PhysRevC.73.014612
|s2cid=118739116
}}</ref><ref>
{{cite journal
|last1=Samanta|first1=C.
|last2=Chowdhury|first2=P. R.
|last3=Basu|first3=D. N.
|year=2007
|title=Predictions of alpha decay half lives of heavy and superheavy elements
|journal=[[Nuclear Physics A]]
|volume=789|issue=1–4|pages=142–154
|arxiv=nucl-th/0703086
|bibcode=2007NuPhA.789..142S
|doi=10.1016/j.nuclphysa.2007.04.001
|citeseerx=10.1.1.264.8177
|s2cid=7496348
}}</ref>
The fission-survived isotope <sup>298</sup>Fl, long expected to be doubly magic, is predicted to have alpha decay half-life ~17 days.<ref name="prc08">
{{cite journal
|last1=Chowdhury|first1=P. R.
|last2=Samanta|first2=C.
|last3=Basu|first3=D. N.
|year=2008
|title=Search for long lived heaviest nuclei beyond the valley of stability
|journal=[[Physical Review C]]
|volume=77|issue=4|page=044603
|arxiv=0802.3837
|bibcode=2008PhRvC..77d4603C
|doi=10.1103/PhysRevC.77.044603
|s2cid=119207807
}}</ref><ref>
{{cite journal
|last1=Roy Chowdhury|first1=P.
|last2=Samanta|first2=C.
|last3=Basu|first3=D. N.
|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> Making <sup>298</sup>Fl directly by a fusion–evaporation pathway is currently impossible: no known combination of target and stable projectile can give 184 neutrons for the compound nucleus, and radioactive projectiles such as <sup>50</sup>Ca (half-life 14&nbsp;s) cannot yet be used in the needed quantity and intensity.<ref name="ZG" /> One possibility for making the theorized long-lived nuclei of copernicium (<sup>291</sup>Cn and <sup>293</sup>Cn) and flerovium near the middle of the island, is using even heavier targets such as <sup>250</sup>[[curium|Cm]], <sup>249</sup>[[berkelium|Bk]], <sup>251</sup>[[californium|Cf]], and <sup>254</sup>[[einsteinium|Es]], that when fused with <sup>48</sup>Ca would yield isotopes such as <sup>291</sup>Mc and <sup>291</sup>Fl (as decay products of <sup>299</sup>Uue, <sup>295</sup>Ts, and <sup>295</sup>Lv), which may have just enough neutrons to alpha decay to nuclides close enough to the centre of the island to possibly undergo electron capture and move inward to the centre. However, reaction cross sections would be small and little is yet known about the decay properties of superheavies near the beta-stability line. This may be the current best hope to synthesize nuclei in the island of stability, but it is speculative and may or may not work in practice.<ref name="Zagrebaev" /> Another possibility is to use controlled [[nuclear explosion]]s to get the high [[neutron flux]] needed to make macroscopic amounts of such isotopes.<ref name="Zagrebaev" /> This would mimic the [[r-process]] where the actinides were first produced in nature and the gap of instability after [[polonium]] bypassed, as it would bypass the gaps of instability at <sup>258–260</sup>[[fermium|Fm]] and at [[mass number]] 275 (atomic numbers [[rutherfordium|104]] to 108).<ref name="Zagrebaev" /> Some such isotopes (especially <sup>291</sup>Cn and <sup>293</sup>Cn) may even have been synthesized in nature, but would decay far too quickly (with half-lives of only thousands of years) and be produced in far too small quantities (~10<sup>−12</sup> the abundance of lead) to be detectable today outside [[cosmic ray]]s.<ref name="Zagrebaev" />

===Atomic and physical===
Flerovium is in group 14 in the [[periodic table]], below [[carbon]], [[silicon]], [[germanium]], [[tin]], and [[lead]]. Every previous group 14 element has 4 electrons in its valence shell, hence [[valence electron]] configuration ns<sup>2</sup>np<sup>2</sup>. For flerovium, the trend will continue and the valence electron configuration is predicted as 7s<sup>2</sup>7p<sup>2</sup>;<ref name="Haire" /> flerovium will be similar to its lighter [[congener (chemistry)|congeners]] in many ways. Differences are likely to arise; a large contributor is [[spin–orbit interaction|spin–orbit (SO) interaction]]—mutual interaction between the electrons' motion and [[Spin (physics)|spin]]. It is especially strong in superheavy elements, because the electrons move faster than in lighter atoms, at speeds comparable to the [[speed of light]].{{sfn|Thayer|2010|pp=63–64}} For flerovium, it lowers the 7s and the 7p electron energy levels<!--|level is an important word. Lv has no 8s electrons but they've been shown to affect its chem---> (stabilizing the corresponding electrons), but two of the 7p electron energy levels are stabilized more than the other four.<ref name="Faegri">
{{Cite journal
|last1=Faegri|first1=K.
|last2=Saue|first2=T.
|date=2001
|title=Diatomic molecules between very heavy elements of group 13 and group 17: A study of relativistic effects on bonding
|journal=[[Journal of Chemical Physics]]
|volume=115|issue=6|page=2456
|bibcode=2001JChPh.115.2456F
|doi=10.1063/1.1385366 
|doi-access=free
}}</ref> The stabilization of the 7s electrons is called the [[inert pair effect]], and the effect "tearing" the 7p subshell into the more and less stabilized parts is called subshell splitting. Computational chemists see the split as a change of the second ([[azimuthal quantum number|azimuthal]]) [[quantum number]] {{mvar|{{ell}}}} from 1 to {{frac|1|2}} and {{frac|3|2}} for the more stabilized and less stabilized parts of the 7p subshell, respectively.{{sfn|Thayer|2010|pp=63–67}}{{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.}} For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s{{su|p=2|w=70%}}7p{{su|b=1/2|p=2|w=70%}}.<ref name="Haire" /> These effects cause flerovium's chemistry to be somewhat different from that of its lighter neighbours.

Because the spin–orbit splitting of the 7p subshell is very large in flerovium, and both of flerovium's filled orbitals in the 7th shell are stabilized relativistically; the valence electron configuration of flerovium may be considered to have a completely filled shell. Its first [[ionization energy]] of {{convert|8.539|eVpar|kJ/mol|abbr=on|lk=on}} should be the second-highest in group 14.<ref name="Haire" /> The 6d electron levels are also destabilized, leading to some early speculations that they may be chemically active, though newer work suggests this is unlikely.<ref name="Fricke1971" /> Because the first ionization energy is higher than in [[silicon]] and [[germanium]], though still lower than in [[carbon]], it has been suggested that flerovium could be classed as a [[metalloid]].<ref name="metalloid">{{cite journal|last1=Gong|first1=Sheng|last2=Wu|first2=Wei|first3=Fancy Qian|last3=Wang|first4=Jie|last4=Liu|first5=Yu|last5=Zhao|first6=Yiheng|last6=Shen|first7=Shuo|last7=Wang|first8=Qiang|last8=Sun|first9=Qian|last9=Wang|date=8 February 2019|title=Classifying superheavy elements by machine learning|journal=Physical Review A|volume=99|issue=2|pages=022110–1–7|doi=10.1103/PhysRevA.99.022110|bibcode=2019PhRvA..99b2110G|hdl=1721.1/120709|s2cid=126792685|hdl-access=free}}</ref>

Flerovium's closed-shell electron configuration means [[metallic bonding]] in metallic flerovium is weaker than in the elements before and after; so flerovium is expected to have a low [[boiling point]],<ref name="Haire" /> and has recently been suggested to be possibly a gaseous metal, similar to predictions for copernicium, which also has a closed-shell electron configuration.<ref name="Kratz" /> Flerovium's [[melting point|melting]] and boiling points were predicted in the 1970s to be around 70 and 150&nbsp;°C,<ref name="Haire" /> significantly lower than for the lighter group 14 elements (lead has 327 and 1749&nbsp;°C), and continuing the trend of decreasing boiling points down the group. Earlier studies predicted a boiling point of ~1000&nbsp;°C or 2840&nbsp;°C,<ref name="Fricke1971" /> but this is now considered unlikely because of the expected weak metallic bonding and that group trends would expect flerovium to have low sublimation enthalpy.<ref name="Haire" /> Preliminary 2021 calculations predicted that flerovium should have melting point −73&nbsp;°C (lower than mercury at −39&nbsp;°C and copernicium, predicted 10&nbsp;±&nbsp;11&nbsp;°C) and boiling point 107&nbsp;°C, which would make it a liquid metal.<ref name=liquid>{{cite journal|last1=Mewes|first1=Jan-Michael|last2=Schwerdtfeger|first2=Peter|date=11 February 2021|title=Exclusively Relativistic: Periodic Trends in the Melting and Boiling Points of Group 12|journal=Angewandte Chemie|volume= 60|issue= 14|pages= 7703–7709|doi=10.1002/anie.202100486|pmid=33576164|pmc=8048430}}</ref> Like [[mercury (element)|mercury]], [[radon]], and [[copernicium]], but not [[lead]] and [[oganesson]] (eka-radon), flerovium is calculated to have no [[electron affinity]].<ref>{{cite web|url=http://www.kernchemie.uni-mainz.de/downloads/che_7/presentations/borschevsky.pdf|title=Fully relativistic ''ab initio'' studies of superheavy elements|last1=Borschevsky|first1=Anastasia|first2=Valeria|last2=Pershina|first3=Uzi|last3=Kaldor|first4=Ephraim|last4=Eliav|website=www.kernchemie.uni-mainz.de|publisher=[[Johannes Gutenberg University Mainz]]|access-date=15 January 2018|archive-url=https://web.archive.org/web/20180115184921/http://www.kernchemie.uni-mainz.de/downloads/che_7/presentations/borschevsky.pdf|archive-date=15 January 2018|url-status=dead|df=dmy-all}}</ref>

A 2010 study published calculations predicting a [[hexagonal close-packed]] crystal structure for flerovium due to spin–orbit coupling effects, and a density of 9.928&nbsp;g/cm<sup>3</sup>, though this was noted to be probably slightly too low.<ref name=hcp>{{cite journal|last1=Hermann|first1=Andreas|last2=Furthmüller|first2=Jürgen|first3=Heinz W.|last3=Gäggeler|first4=Peter|last4=Schwerdtfeger|date=2010|title=Spin-orbit effects in structural and electronic properties for the solid state of the group-14 elements from carbon to superheavy element 114|journal=Physical Review B|volume=82|issue=15|pages=155116–1–8|doi=10.1103/PhysRevB.82.155116|bibcode=2010PhRvB..82o5116H|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A15511}}</ref> Newer calculations published in 2017 expected flerovium to crystallize in [[face-centred cubic]] crystal structure like its lighter congener lead,<ref name=fcc>{{cite journal|last1=Maiz Hadj Ahmed|first1=H.|last2=Zaoui|first2=A.|last3=Ferhat|first3=M.|date=2017|title=Revisiting the ground state phase stability of super-heavy element Flerovium|journal=Cogent Physics|volume=4|issue=1|doi=10.1080/23311940.2017.1380454|bibcode=2017CogPh...4m8045M|s2cid=125920084|doi-access=free}}</ref> and calculations published in 2022 predicted a density of 11.4&nbsp;±&nbsp;0.3&nbsp;g/cm<sup>3</sup>, similar to lead (11.34&nbsp;g/cm<sup>3</sup>). These calculations found that the face-centred cubic and hexagonal close-packed structures should have nearly the same energy, a phenomenon reminiscent of the noble gases. These calculations predict that hexagonal close-packed flerovium should be a semiconductor, with a [[band gap]] of 0.8&nbsp;±&nbsp;0.3&nbsp;eV. (Copernicium is also predicted to be a semiconductor.) These calculations predict that the cohesive energy of flerovium should be around −0.5&nbsp;±&nbsp;0.1&nbsp;eV; this is similar to that predicted for oganesson (−0.45&nbsp;eV), larger than that predicted for copernicium (−0.38&nbsp;eV), but smaller than that of mercury (−0.79&nbsp;eV). The melting point was calculated as 284&nbsp;±&nbsp;50&nbsp;K (11&nbsp;±&nbsp;50&nbsp;°C), so that flerovium is probably a liquid at room temperature, although the boiling point was not determined.<ref name=Florez/>

The electron of a [[hydrogen-like atom|hydrogen-like]] flerovium ion (Fl<sup>113+</sup>; remove all but one electron) is expected to move so fast that its mass is 1.79 times that of a stationary electron, due to [[relativistic quantum chemistry|relativistic effects]]. (The figures for hydrogen-like lead and tin are expected to be 1.25 and 1.073 respectively.{{sfn|Thayer|2010|pp=64}}) Flerovium would form weaker metal–metal bonds than lead and would be [[adsorption|adsorbed]] less on surfaces.{{sfn|Thayer|2010|pp=64}}

===Chemical===
Flerovium is the heaviest known member of group 14, below lead, and is projected to be the second member of the 7p series of elements. Nihonium and flerovium are expected to form a very short subperiod corresponding to the filling of the 7p<sub>1/2</sub> orbital, coming between the filling of the 6d<sub>5/2</sub> and 7p<sub>3/2</sub> subshells. Their chemical behaviour is expected to be very distinctive: nihonium's homology to thallium has been called "doubtful" by computational chemists, while flerovium's to lead has been called only "formal".<ref name="Zaitsevskii">{{cite web|url=http://tan11.jinr.ru/pdf/07_Sep/S_3/04_Titov.pdf|title=Relativistic DFT and ab initio calculations on the seventh-row superheavy elements: E113 - E114|last1=Zaitsevskii|first1=A.|first2=C.|last2=van Wüllen|first3=A.|last3=Rusakov|first4=A.|last4=Titov|date=September 2007|website=jinr.ru|access-date=17 February 2018}}</ref>

The first five group 14 members show a +4 oxidation state and the latter members have increasingly prominent +2 chemistry due to onset of the inert pair effect. For tin, the +2 and +4 states are similar in stability, and lead(II) is the most stable of all the chemically well-understood +2 oxidation states in group 14.<ref name="Haire" /> The 7s orbitals are very highly stabilized in flerovium, so a very large sp<sup>3</sup> [[orbital hybridization]] is needed to achieve a +4 oxidation state, so flerovium is expected to be even more stable than lead in its strongly predominant +2 oxidation state and its +4 oxidation state should be highly unstable.<ref name="Haire" /> For example, the dioxide (FlO<sub>2</sub>) is expected to be highly unstable to decomposition into its constituent elements (and would not be formed by direct reaction of flerovium with oxygen),<ref name="Haire" />{{sfn|Pershina|2010|p=502}} and flerovane (FlH<sub>4</sub>), which should have Fl–H bond lengths of 1.787&nbsp;[[angstrom|Å]]<ref name="Schwerdtfeger" /> and would be the heaviest homologue of [[methane]] (the lighter compounds include [[silane]], [[germane]] and [[stannane]]), is predicted to be more thermodynamically unstable than [[plumbane]], spontaneously decomposing to flerovium(II) hydride (FlH<sub>2</sub>) and H<sub>2</sub>.{{sfn|Pershina|2010|p=503}} The tetrafluoride FlF<sub>4</sub>{{sfn|Thayer|2010|p=83}} would have bonding mostly due to ''sd'' hybridizations rather than ''sp''<sup>3</sup> hybridizations,<ref name="Fricke1971">{{cite journal|last1=Fricke|first1=B.|last2=Greiner|first2=W.|last3=Waber|first3=J. T.|date=1971|title=The continuation of the periodic table up to Z = 172. The chemistry of superheavy elements|journal=Theoretica Chimica Acta|volume=21|issue=3|pages=235–260|doi=10.1007/BF01172015|s2cid=117157377|url=https://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008081923380/1/Fricke_continuation_1971.pdf|archive-date=4 March 2016|access-date=20 April 2018|archive-url=https://web.archive.org/web/20160304200000/https://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008081923380/1/Fricke_continuation_1971.pdf|url-status=dead}}</ref> and its decomposition to the difluoride and fluorine gas would be exothermic.<ref name="Schwerdtfeger" /> The other tetrahalides (for example, FlCl<sub>4</sub> is destabilized by about 400&nbsp;kJ/mol) decompose similarly.<ref name="Schwerdtfeger" /> The corresponding polyfluoride anion {{chem|FlF|6|2-}} should be unstable to [[hydrolysis]] in aqueous solution, and flerovium(II) polyhalide anions such as {{chem|FlBr|3|-}} and {{chem|FlI|3|-}} are predicted to form preferentially in solutions.<ref name="Haire" /> The ''sd'' hybridizations were suggested in early calculations, as flerovium's 7s and 6d electrons share about the same energy, which would allow a volatile [[hexafluoride]] to form, but later calculations do not confirm this possibility.<ref name="Fricke1971" /> In general, spin–orbit contraction of the 7p<sub>1/2</sub> orbital should lead to smaller bond lengths and larger bond angles: this has been theoretically confirmed in FlH<sub>2</sub>.<ref name="Schwerdtfeger" /> Still, even FlH<sub>2</sub> should be relativistically destabilized by 2.6&nbsp;eV to below Fl+H<sub>2</sub>; the large spin–orbit effects also break down the usual singlet–triplet divide in the group 14 dihydrides. FlF<sub>2</sub> and FlCl<sub>2</sub> are predicted to be more stable than FlH<sub>2</sub>.<ref>{{cite journal|last1=Balasubramanian|first1=K.|date=30 July 2002|title=Breakdown of the singlet and triplet nature of electronic states of the superheavy element 114 dihydride (114H<sub>2</sub>)|journal=Journal of Chemical Physics|volume=117|issue=16|pages=7426–32|doi=10.1063/1.1508371|bibcode=2002JChPh.117.7426B}}</ref>

Due to relativistic stabilization of flerovium's 7s<sup>2</sup>7p{{su|b=1/2|p=2|w=70%}} valence electron configuration, the 0 oxidation state should also be more stable for flerovium than for lead, as the 7p<sub>1/2</sub> electrons begin to also have a mild inert pair effect:<ref name="Haire" /> this stabilization of the neutral state may bring about some similarities between the behavior of flerovium and the noble gas [[radon]].<ref name="tanm" /> Due to flerovium's expected relative inertness, diatomic compounds FlH and FlF should have lower energies of [[dissociation (chemistry)|dissociation]] than the corresponding [[lead]] compounds PbH and PbF.<ref name="Schwerdtfeger" /> Flerovium(IV) should be even more electronegative than lead(IV);{{sfn|Thayer|2010|p=83}} lead(IV) has electronegativity 2.33 on the Pauling scale, though the lead(II) value is only 1.87. Flerovium could be a [[noble metal]].<ref name="Haire" />

Flerovium(II) should be more stable than lead(II), and halides FlX<sup>+</sup>, FlX<sub>2</sub>, {{chem|FlX|3|-}}, and {{chem|FlX|4|2-}} (X = [[chlorine|Cl]], [[bromine|Br]], [[iodine|I]]) are expected to form readily. The fluorides would undergo strong hydrolysis in aqueous solution.<ref name="Haire" /> All flerovium dihalides are expected to be stable;<ref name="Haire" /> the difluoride being water-soluble.<ref name="webelements">{{cite web|last=Winter|first=M.|date=2012|title=Flerovium: The Essentials|url=http://webelements.com/flerovium/|website=WebElements|publisher=[[University of Sheffield]]|access-date=28 August 2008}}</ref> Spin–orbit effects would destabilize the dihydride (FlH<sub>2</sub>) by almost {{convert|2.6|eVpar|kJ/mol|abbr=on}}.{{sfn|Pershina|2010|p=502}} In aqueous solution, the [[oxyanion]] flerovite ({{chem|FlO|2|2-}}) would also form, analogous to [[plumbite]]. Flerovium(II) sulfate (FlSO<sub>4</sub>) and sulfide (FlS) should be very insoluble in water, and flerovium(II) [[acetate]] (Fl(C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>)<sub>2</sub>) and nitrate (Fl(NO<sub>3</sub>)<sub>2</sub>) should be quite water-soluble.<ref name="Fricke1971" /> The [[standard electrode potential]] for [[redox|reduction]] of Fl<sup>2+</sup> ion to metallic flerovium is estimated to be around +0.9&nbsp;V, confirming the increased stability of flerovium in the neutral state.<ref name="Haire" /> In general, due to relativistic stabilization of the 7p<sub>1/2</sub> spinor, Fl<sup>2+</sup> is expected to have properties intermediate between those of [[mercury (element)|Hg]]<sup>2+</sup> or [[cadmium|Cd]]<sup>2+</sup> and its lighter congener Pb<sup>2+</sup>.<ref name="Haire" />