Editing Periodic table (section)

== Future extension beyond the seventh period ==
{{Main|Extended periodic table}}
{{See also|Island of stability}}
[[File:Energy eigenvalues superheavy.svg|thumb|right|512px|Energy eigenvalues (in eV) for the outermost electrons of elements with Z = 100 through 172, predicted using Dirac–Fock calculations. The − and + signs refer to orbitals with decreased or increased azimuthal quantum number from spin–orbit splitting respectively: p− is p<sub>1/2</sub>, p+ is p<sub>3/2</sub>, d− is d<sub>3/2</sub>, d+ is d<sub>5/2</sub>, f− is f<sub>5/2</sub>, f+ is f<sub>7/2</sub>, g− is g<sub>7/2</sub>, and g+ is g<sub>9/2</sub>.<ref name=BFricke/> The spacing of energy levels up to ''Z'' = 120 is normal, and becomes normal again at ''Z'' = 157; between them, a very different situation is observed.<ref name=BFricke1977/>]]
The most recently named elements – nihonium (113), moscovium (115), tennessine (117), and oganesson (118) – completed the seventh row of the periodic table.<ref name="IUPAC-redbook" /> Future elements would have to begin an [[period 8 element|eighth row]]. These elements may be referred to either by their atomic numbers (e.g. "[[Extended periodic table|element 164]]"), or by the IUPAC [[systematic element name]]s adopted in 1978, which directly relate to the atomic numbers (e.g. "unhexquadium" for element 164, derived from Latin ''unus'' "one", Greek ''hexa '' "six", Latin ''quadra'' "four", and the traditional ''-ium'' suffix for metallic elements).<ref name="IUPAC-redbook" /> All attempts to synthesize such elements have failed so far. An attempt to make [[Ununennium|element 119]] has been ongoing since 2018 at the Riken research institute in Japan. The LBNL in the United States, the JINR in Russia, and the Heavy Ion Research Facility in [[Lanzhou]] (HIRFL) in China also plan to make their own attempts at synthesizing the first few period 8 elements.<ref name="nature2019">{{cite journal |last=Ball |first=P. |title=Extreme chemistry: experiments at the edge of the periodic table |date=2019 |journal=Nature |volume=565 |issue=7741 |pages=552–555 |issn=1476-4687 |doi=10.1038/d41586-019-00285-9|pmid=30700884 |bibcode=2019Natur.565..552B |doi-access=free }}</ref><ref name="SHEfactory">{{cite conference |url=https://www.epj-conferences.org/articles/epjconf/pdf/2016/26/epjconf-NS160-08001.pdf |title=Status and perspectives of the Dubna superheavy element factory |last1=Dmitriev |first1=Sergey |last2=Itkis |first2=Mikhail |last3=Oganessian |first3=Yuri |date=2016 |conference=Nobel Symposium NS160 – Chemistry and Physics of Heavy and Superheavy Elements |doi=10.1051/epjconf/201613108001 |access-date=15 August 2021 |archive-date=28 August 2021 |archive-url=https://web.archive.org/web/20210828071031/https://www.epj-conferences.org/articles/epjconf/pdf/2016/26/epjconf-NS160-08001.pdf |url-status=live }}</ref><ref>{{cite web |url=https://www.jinr.ru/posts/how-are-new-chemical-elements-born/ |title=How are new chemical elements born? |last1=Sokolova |first1=Svetlana |last2=Popeko |first2=Andrei |date=24 May 2021 |website=jinr.ru |publisher=JINR |access-date=4 November 2021 |quote= |archive-date=4 November 2021 |archive-url=https://web.archive.org/web/20211104173902/https://www.jinr.ru/posts/how-are-new-chemical-elements-born/ |url-status=live }}</ref><ref>{{cite news |last=Chapman |first=Kit |date=10 October 2023 |title=Berkeley Lab to lead US hunt for element 120 after breakdown of collaboration with Russia |url=https://www.chemistryworld.com/news/berkeley-lab-to-lead-us-hunt-for-element-120-after-breakdown-of-collaboration-with-russia/4018207.article |work=Chemistry World |location= |access-date=20 October 2023}}</ref><ref>{{cite web |url=https://physicalsciences.lbl.gov/2023/10/16/berkeley-lab-to-test-new-approach-to-making-superheavy-elements/ |title=Berkeley Lab to Test New Approach to Making Superheavy Elements |last=Biron |first=Lauren |date=16 October 2023 |website=lbl.gov |publisher=[[Lawrence Berkeley National Laboratory]] |access-date=20 October 2023 |quote=}}</ref><ref>{{cite journal |last1=Gan |first1=Z. G. |last2=Huang |first2=W. X. |last3=Zhang |first3=Z. Y. |last4=Zhou |first4=X. H. |last5=Xu |first5=H. S. |date=2022 |title=Results and perspectives for study of heavy and super-heavy nuclei and elements at IMP/CAS |url= |journal=The European Physical Journal A |volume=58 |issue=158 |pages= |doi=10.1140/epja/s10050-022-00811-w |bibcode=2022EPJA...58..158G |access-date=}}</ref>

If the eighth period followed the pattern set by the earlier periods, then it would contain fifty elements, filling the 8s, {{Not a typo|5g}}, 6f, 7d, and finally 8p subshells in that order. But by this point, relativistic effects should result in significant deviations from the Madelung rule. Various different models have been suggested for the configurations of eighth-period elements, as well as how to show the results in a periodic table. All agree that the eighth period should begin like the previous ones with two 8s elements, 119 and [[unbinilium|120]]. However, after that the massive energetic overlaps between the {{Not a typo|5g}}, 6f, 7d, and 8p subshells means that they all begin to fill together, and it is not clear how to separate out specific {{not a typo|5g}} and 6f series.<ref name="nefedov">{{cite journal |last1=Nefedov |first1=V.I. |last2=Trzhaskovskaya |first2=M.B. |last3=Yarzhemskii |first3=V.G. |title=Electronic Configurations and the Periodic Table for Superheavy Elements |journal=Doklady Physical Chemistry |date=2006 |volume=408 |issue=2 |pages=149–151 |doi=10.1134/S0012501606060029 |s2cid=95738861 |issn=0012-5016 |url=https://www.primefan.ru/stuff/chem/nefedov.pdf |access-date=15 August 2021 |archive-date=13 October 2016 |archive-url=https://web.archive.org/web/20161013113837/https://www.primefan.ru/stuff/chem/nefedov.pdf |url-status=live }}</ref><ref name=recentattempts>{{cite journal |last1=Scerri |first1=Eric |date=2020 |title=Recent attempts to change the periodic table |journal=Philosophical Transactions of the Royal Society A |volume=378 |issue=2180 |doi=10.1098/rsta.2019.0300|pmid=32811365 |bibcode=2020RSPTA.37890300S |s2cid=221136189 |doi-access=free }}</ref><ref>{{cite journal|doi=10.2307/3963006|last=Frazier|first=K.|title=Superheavy Elements|journal=Science News|volume=113|issue=15|pages=236–38|year=1978|jstor=3963006}}</ref><ref name="Fricke">{{cite journal |last1=Fricke |first1=B. |last2=Greiner |first2=W. |last3=Waber |first3=J. T. |year=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=235–60 |doi=10.1007/BF01172015 |s2cid=117157377 }}</ref><ref name="PT172">{{Cite journal|last1=Pyykkö|first1=P.|author-link=Pekka Pyykkö|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=161–68|year=2011|pmid=20967377|doi=10.1039/c0cp01575j|bibcode=2011PCCP...13..161P|s2cid=31590563}}</ref> Elements [[unbiunium|121]] through 156 thus do not fit well as chemical analogues of any previous group in the earlier parts of the table,<ref name=actrev/> although they have sometimes been placed as {{not a typo|5g}}, 6f, and other series to formally reflect their electron configurations.<ref name=actrev/> Eric Scerri has raised the question of whether an extended periodic table should take into account the failure of the Madelung rule in this region, or if such exceptions should be ignored.<ref name=recentattempts /> The shell structure may also be fairly formal at this point: already the electron distribution in an oganesson atom is expected to be rather uniform, with no discernible shell structure.<ref name="oganesson-elf">{{cite journal| journal=Phys. Rev. Lett.| volume=120| issue=5| page=053001| date=2018| title=Electron and Nucleon Localization Functions of Oganesson: Approaching the Thomas-Fermi Limit| first1=Paul |last1=Jerabek |first2=Bastian |last2=Schuetrumpf |first3=Peter |last3=Schwerdtfeger |first4=Witold |last4=Nazarewicz| doi=10.1103/PhysRevLett.120.053001| pmid=29481184| arxiv = 1707.08710 | bibcode = 2018PhRvL.120e3001J| s2cid=3575243}}</ref>

The situation from elements 157 to 172 should return to normalcy and be more reminiscent of the earlier rows.<ref name=BFricke1977/> The heavy p-shells are split by the [[spin–orbit interaction]]: one p&nbsp;orbital (p<sub>1/2</sub>) is more stabilized, and the other two (p<sub>3/2</sub>) are destabilized. (Such shifts in the quantum numbers happen for all types of shells, but it makes the biggest difference to the order for the p-shells.) It is likely that by element 157, the filled 8s and 8p<sub>1/2</sub> shells with four electrons in total have sunk into the core. Beyond the core, the next orbitals are 7d and 9s at similar energies, followed by 9p<sub>1/2</sub> and 8p<sub>3/2</sub> at similar energies, and then a large gap.<ref name="BFricke1977">{{cite journal |last1=Fricke |first1=Burkhard |year=1977 |title=Dirac–Fock–Slater calculations for the elements Z = 100, fermium, to Z = 173 |journal=Recent Impact of Physics on Inorganic Chemistry |volume=19 |pages=83–192 |doi=10.1016/0092-640X(77)90010-9 |url=http://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008071622807/1/Fricke_Dirac_1977.pdf |access-date=25 February 2016 |bibcode=1977ADNDT..19...83F |archive-date=22 March 2016 |archive-url=https://web.archive.org/web/20160322072636/http://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008071622807/1/Fricke_Dirac_1977.pdf |url-status=dead }}</ref> Thus, the 9s and 9p<sub>1/2</sub> orbitals in essence replace the 8s and 8p<sub>1/2</sub> ones, making elements 157–172 probably chemically analogous to groups 3–18: for example, element 164 would appear two places below lead in group 14 under the usual pattern, but is calculated to be very analogous to palladium in group 10 instead.<ref name=rareearths/><ref name=Fricke/><ref name=nefedov/><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><ref name=actrev>{{cite journal |last1=Fricke |first1=Burkhard |last2=Waber |first2=J. T. |date=1971 |title=Theoretical Predictions of the Chemistry of Superheavy Elements: Continuation of the Periodic Table up to Z{{=}}184 |url=https://kobra.uni-kassel.de/bitstream/handle/123456789/2008100124269/Fricke_theoretical_1971.pdf |journal=Actinides Reviews |volume=1 |issue= |pages=433–485 |doi= |access-date=5 January 2024}}</ref> Thus, it takes fifty-four elements rather than fifty to reach the next noble element after 118.<ref name=wothers>{{cite book |last=Wothers |first=Peter |author-link= |date=2019 |title=Antimony, Gold, and Jupiter's Wolf |url= |location= |publisher=Oxford University Press |page=vii |isbn=978-0-19-965272-3}}</ref> However, while these conclusions about elements 157 through 172's chemistry are generally agreed by models,<ref name=actrev/><ref name=nefedov/> there is disagreement on whether the periodic table should be drawn to reflect chemical analogies, or if it should reflect likely formal electron configurations, which should be quite different from earlier periods and are not agreed between sources. Discussion about the format of the eighth row thus continues.<ref name=nefedov/><ref name=Fricke/><ref name=PT172/><ref name=smits>{{cite journal |last1=Smits |first1=Odile R. |last2=Düllmann |first2=Christoph E. |last3=Indelicato |first3=Paul |last4=Nazarewicz |first4=Witold |last5=Schwerdtfeger |first5=Peter |date=2023 |title=The quest for superheavy elements and the limit of the periodic table |url= |journal=Nature Reviews Physics |volume= 6|issue= 2|pages= 86–98|doi=10.1038/s42254-023-00668-y |osti=2315603 |s2cid=266276980 |access-date=}}</ref>

Beyond element 172, calculation is complicated by the 1s electron energy level becoming [[imaginary number|imaginary]]. Such a situation does have a physical interpretation and does not in itself pose an electronic limit to the periodic table, but the correct way to incorporate such states into multi-electron calculations is still an open question needing to be solved to calculate the periodic table's structure beyond this point.<ref name=gamowstates>{{cite journal |last1=Smits |first1=O. R. |last2=Indelicato |first2=P. |first3=W. |last3=Nazarewicz |first4=M. |last4=Piibeleht |first5=P. |last5=Schwerdtfeger |date=2023 |title=Pushing the limits of the periodic table—A review on atomic relativistic electronic structure theory and calculations for the superheavy elements |url= |journal=Physics Reports |volume=1035 |issue= |pages=1–57 |doi=10.1016/j.physrep.2023.09.004 |arxiv=2301.02553 |bibcode=2023PhR..1035....1S |access-date=}}</ref>

Nuclear stability will likely prove a decisive factor constraining the number of possible elements. It depends on the balance between the electric repulsion between protons and the strong force binding protons and neutrons together.<ref>{{cite journal |last1=Pershina |first1=Valeria |date=2020 |title=Relativistic effects on the electronic structure of the heaviest elements. Is the Periodic Table endless? |url=https://comptes-rendus.academie-sciences.fr/chimie/article/CRCHIM_2020__23_3_255_0.pdf |journal=Comptes Rendus Chimie |volume=23 |issue=3 |pages=255–265 |doi=10.5802/crchim.25 |s2cid=222225772 |access-date=28 March 2021 |archive-date=11 December 2020 |archive-url=https://web.archive.org/web/20201211103843/https://comptes-rendus.academie-sciences.fr/chimie/article/CRCHIM_2020__23_3_255_0.pdf |url-status=live }}</ref> Protons and neutrons are arranged in [[nuclear shell model|shells]], just like electrons, and so a closed shell can significantly increase stability: the known superheavy nuclei exist because of such a shell closure, probably at around 114–[[unbihexium|126]] protons and 184 neutrons.<ref name=gamowstates/> They are probably close to a predicted [[island of stability]], where superheavy nuclides should be more long-lived than expected: predictions for the longest-lived nuclides on the island range from microseconds to millions of years.<ref name=smits/><ref name="physorg">{{cite web |url=https://newscenter.lbl.gov/2009/09/24/114-confirmed/ |title=Superheavy Element 114 Confirmed: A Stepping Stone to the Island of Stability |date=2009 |access-date=23 October 2019 |publisher=[[Lawrence Berkeley National Laboratory|Berkeley Lab]] |archive-date=20 July 2019 |archive-url=https://web.archive.org/web/20190720200414/https://newscenter.lbl.gov/2009/09/24/114-confirmed/ |url-status=live }}</ref><ref name="nuclei">{{cite journal |last=Oganessian |first=Yu. Ts. |year=2012 |title=Nuclei in the "Island of Stability" of Superheavy Elements |journal=[[Journal of Physics: Conference Series]] |volume=337 |issue=1 |page=012005 |bibcode=2012JPhCS.337a2005O |doi=10.1088/1742-6596/337/1/012005|doi-access=free }}</ref> It should nonetheless be noted that these are essentially extrapolations into an unknown part of the chart of nuclides, and systematic model uncertainties need to be taken into account.<ref name=smits/>

As the closed shells are passed, the stabilizing effect should vanish.<ref name=relqed/> Thus, superheavy nuclides with more than 184 neutrons are expected to have much shorter lifetimes, spontaneously fissioning within 10<sup>−15</sup>&nbsp;seconds. If this is so, then it would not make sense to consider them chemical elements: [IUPAC/IUPAP theorizes and recommends] an element to exist only if the nucleus lives longer than 10<sup>−14</sup>&nbsp;seconds, the time needed for it to gather an electron cloud. Nonetheless, theoretical estimates of half-lives are very model-dependent, ranging over many orders of magnitude.<ref name=gamowstates/> The extreme repulsion between protons is predicted to result in exotic nuclear topologies, with bubbles, rings, and tori expected: this further complicates extrapolation.<ref name=smits/> It is not clear if any further-out shell closures exist, due to an expected smearing out of distinct nuclear shells (as is already expected for the electron shells at oganesson).<ref name=relqed>{{cite journal |last1=Schwerdtfeger |first1=Peter |last2=Pašteka |first2=Lukáš F. |last3=Punnett |first3=Andrew |last4=Bowman |first4=Patrick O. |date=2015 |title=Relativistic and quantum electrodynamic effects in superheavy elements |journal=Nuclear Physics A |volume=944 |issue=December 2015 |pages=551–577 |doi=10.1016/j.nuclphysa.2015.02.005|bibcode=2015NuPhA.944..551S }}</ref> Furthermore, even if later shell closures exist, it is not clear if they would allow such heavy elements to exist.<ref name="greinernuclei">{{cite journal|last=Greiner|first=W.|date=2013|title=Nuclei: superheavy-superneutronic-strange-and of antimatter|url=https://inspirehep.net/record/1221632/files/jpconf13_413_012002.pdf|journal=Journal of Physics: Conference Series|volume=413|issue=1|pages=012002-1–012002-9<!-- Deny Citation Bot-->|doi=10.1088/1742-6596/413/1/012002|bibcode=2013JPhCS.413a2002G|doi-access=free|access-date=15 August 2021|archive-date=30 March 2019|archive-url=https://web.archive.org/web/20190330183222/https://inspirehep.net/record/1221632/files/jpconf13_413_012002.pdf|url-status=live}}</ref><ref name="radiochimica">{{cite journal |last1=Hofmann |first1=Sigurd |date=2019 |title=Synthesis and properties of isotopes of the transactinides |journal=Radiochimica Acta |volume=107 |issue=9–11 |pages=879–915 |doi=10.1515/ract-2019-3104|s2cid=203848120 }}</ref><ref name="PTSS1">Scerri, p. 386</ref><ref name="EB">{{cite encyclopedia|last1=Seaborg|first1=G.|url=https://www.britannica.com/EBchecked/topic/603220/transuranium-element|title=transuranium element (chemical element)|encyclopedia=Encyclopædia Britannica|date=c. 2006|access-date=16 March 2010|url-status=live|archive-url=https://web.archive.org/web/20101130112151/https://www.britannica.com/EBchecked/topic/603220/transuranium-element|archive-date=30 November 2010}}</ref> As such, it may be that the periodic table practically ends around element 120, as elements become too short-lived to observe, and then too short-lived to have chemistry; the era of discovering new elements would thus be close to its end.<ref name="EB"/><ref>{{cite journal |author=Peter Möller |url=https://www.epj-conferences.org/articles/epjconf/abs/2016/26/epjconf-NS160-03002/epjconf-NS160-03002.html |title=The limits of the nuclear chart set by fission and alpha decay {{pipe}} EPJ Web of Conferences |journal=European Physical Journal Web of Conferences |year=2016 |doi=10.1051/epjconf/201613103002 |publisher=Epj-conferences.org |volume=131 |page=03002 |bibcode=2016EPJWC.13103002M |access-date=13 June 2022 |archive-date=20 June 2022 |archive-url=https://web.archive.org/web/20220620210806/https://www.epj-conferences.org/articles/epjconf/abs/2016/26/epjconf-NS160-03002/epjconf-NS160-03002.html |url-status=live |doi-access=free }}</ref> If another proton shell closure beyond 126 does exist, then it probably occurs around 164;<ref name=greinernuclei/> thus the region where periodicity fails more or less matches the region of instability between the shell closures.<ref name=actrev/>

Alternatively, [[quark matter]] may become stable at high mass numbers, in which the nucleus is composed of freely flowing [[up quark|up]] and [[down quark]]s instead of binding them into protons and neutrons; this would create a [[continent of stability]] instead of an island.<ref name="udQM">{{cite journal |last1=Holdom |first1=B. |last2=Ren |first2=J. |last3=Zhang |first3=C. |title=Quark matter may not be strange |date=2018 |journal=Physical Review Letters |volume=120 |issue=1 |pages=222001-1–222001-6 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevLett.120.222001|pmid=29906186 |arxiv=1707.06610 |bibcode=2018PhRvL.120v2001H |s2cid=49216916 }}</ref><ref name="udQMnew">{{cite journal |last1=Cheng-Jun |first1=Xia |last2=She-Sheng |first2=Xue |last3=Ren-Xin |first3=Xu |last4=Shan-Gui |first4=Zhou |title=Supercritically charged objects and electron-positron pair creation |doi=10.1103/PhysRevD.101.103031 |journal=Physical Review D |year=2020 |volume=101 |issue=10 |page=103031|arxiv=2001.03531 |bibcode=2020PhRvD.101j3031X |s2cid=210157134 }}</ref> Other effects may come into play: for example, in very heavy elements the 1s electrons are likely to spend a significant amount of time so close to the nucleus that they are actually inside it, which would make them vulnerable to [[electron capture]].<ref name=colloq>{{cite journal |title=Colloquium: Superheavy elements: Oganesson and beyond |first1=S. A. |last1=Giuliani |first2=Z. |last2=Matheson |first3=W. |last3=Nazarewicz |first4=E. |last4=Olsen |first5=P.-G. |last5=Reinhard |first6=J. |last6=Sadhukhan |first7=B. |last7=Schtruempf |first8=N. |last8=Schunck |first9=P. |last9=Schwerdtfeger |date=2019 |journal=Reviews of Modern Physics |volume=91 |issue=1 |pages=011001-1–011001-25 |doi=10.1103/RevModPhys.91.011001|bibcode=2019RvMP...91a1001G |s2cid=126906074 |doi-access=free }}</ref>

Even if eighth-row elements can exist, producing them is likely to be difficult, and it should become even more difficult as atomic number rises.<ref>{{cite journal|last1=Giardina|first1=G.|last2=Fazio|first2=G.|last3=Mandaglio|first3=G.|last4=Manganaro|first4=M.|last5=Nasirov|first5=A.K.|last6=Romaniuk|first6=M.V.|last7=Saccà|first7=C.|title=Expectations and limits to synthesize nuclei with Z ≥ 120|date=2010|journal=International Journal of Modern Physics E|volume=19|issue=5 & 6|pages=882–893|doi=10.1142/S0218301310015333|url=https://www.researchgate.net/publication/263915732|bibcode=2010IJMPE..19..882G|access-date=15 August 2021|archive-date=19 October 2021|archive-url=https://web.archive.org/web/20211019202251/https://www.researchgate.net/publication/263915732_EXPECTATIONS_AND_LIMITS_TO_SYNTHESIZE_NUCLEI_WITH_Z_120|url-status=live}}</ref> Although the 8s elements 119 and 120 are expected to be reachable with present means, the elements beyond that are expected to require new technology,<ref name="Zagrebaev">{{cite journal|title=Future of superheavy element research: Which nuclei could be synthesized within the next few years?|url=https://nrv.jinr.ru/pdf_file/J_phys_2013.pdf|first1=Valeriy|last1=Zagrebaev|first2=Alexander|last2=Karpov|first3=Walter|last3=Greiner|date=2013|journal=Journal of Physics|volume=420|issue=1|page=012001|publisher=IOP Publishing Ltd.|doi=10.1088/1742-6596/420/1/012001|arxiv=1207.5700|bibcode=2013JPhCS.420a2001Z|s2cid=55434734|access-date=1 December 2020|archive-date=3 October 2015|archive-url=https://web.archive.org/web/20151003154020/https://nrv.jinr.ru/pdf_file/J_phys_2013.pdf|url-status=live}}</ref> if they can be produced at all.<ref name="Bloomberg">{{cite web|last=Subramanian|first=S.|author-link=Samanth Subramanian|date=2019|url=https://www.bloomberg.com/news/features/2019-08-28/making-new-elements-doesn-t-pay-just-ask-this-berkeley-scientist|title=Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist|website=[[Bloomberg Businessweek]]|access-date=18 January 2020|archive-date=11 December 2019|archive-url=https://web.archive.org/web/20191211191525/https://www.bloomberg.com/news/features/2019-08-28/making-new-elements-doesn-t-pay-just-ask-this-berkeley-scientist|url-status=live}}</ref> Experimentally characterizing these elements chemically would also pose a great challenge.<ref name="nature2019" />