Editing Extended periodic table (section)

==Predicted structures of an extended periodic table==
There is currently no consensus on the placement of elements beyond [[unbinilium|atomic number 120]] in the periodic table.

All hypothetical elements are given an [[International Union of Pure and Applied Chemistry]] (IUPAC) [[systematic element name]], for use until the element has been discovered, confirmed, and an official name is approved. These names are typically not used in the literature, and the elements are instead referred to by their atomic numbers; hence, element 164 is usually not called "unhexquadium" or "Uhq" (the systematic name and symbol), but rather "element 164" with symbol "164", "(164)", or "E164".<ref name=Haire/>

===Aufbau principle===
At element 118, the orbitals 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 7s and 7p are assumed to be filled, with the remaining orbitals unfilled. A simple extrapolation from the [[Aufbau principle]] would predict the eighth row to fill orbitals in the order 8s, 5g, 6f, 7d, 8p; but after element 120, the proximity of the electron shells makes placement in a simple table problematic.
{{Extended periodic table (by Aufbau, 50 columns, compact)}}

===Fricke===
Not all models show the higher elements following the pattern established by lighter elements. Burkhard Fricke et al., who carried out calculations up to element 184 in an article published in 1971, also found some elements to be displaced from the [[Aufbau principle|Madelung energy-ordering rule]] as a result of overlapping orbitals; this is caused by the increasing role of [[relativistic quantum chemistry|relativistic effects]] in heavy elements (They describe chemical properties up to element 184, but only draw a table to element 172.)<ref name="Fricke"/><ref name="BFricke"/>
{| class="wikitable" style="text-align: center;"
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| Ga
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| As
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| Br
| Kr
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| Sr
| Y
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| Nb
| Mo
| Tc
| Ru
| Rh
| Pd
| Ag
| Cd
| In
| Sn
| Sb
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| I
| Xe
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| Cs
| Ba
| La
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| Ce–Lu
| Hf
| Ta
| W
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| Pt
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| Hg
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| Rf
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| Bh
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| Mt
| Ds
| Rg
| Cn
| Nh
| Fl
| Mc
| Lv
| Ts
| Og
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| 119
| 120
| 121
| {{nowrap|122–141}}
| 142–155
| 156
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Fricke et al.'s format is more focused on formal electron configurations than likely chemical behaviour. They place elements 156–164 in groups 4–12 because formally their configurations should be 7d<sup>2</sup> through 7d<sup>10</sup>. However, they differ from the previous d-elements in that the 8s shell is not available for chemical bonding: instead, the 9s shell is. Thus element 164 with 7d<sup>10</sup>9s<sup>0</sup> is noted by Fricke et al. to be analogous to palladium with 4d<sup>10</sup>5s<sup>0</sup>, and they consider elements 157–172 to have chemical analogies to groups 3–18 (though they are ambivalent on whether elements 165 and 166 are more like group 1 and 2 elements or more like group 11 and 12 elements, respectively). Thus, elements 157–164 are placed in their table in a group that the authors do not think is chemically most analogous.<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>

===Nefedov===
{{ill|Vadim Nefedov|lt=Nefedov|ru|Нефёдов, Вадим Иванович}}, Trzhaskovskaya, and Yarzhemskii carried out calculations up to 164 (results published in 2006). They considered elements 158 through 164 to be homologues of groups 4 through 10, and not 6 through 12, noting similarities of electron configurations to the period 5 transition metals (e.g. element 159 7d<sup>4</sup>9s<sup>1</sup> vs Nb 4d<sup>4</sup>5s<sup>1</sup>, element 160 7d<sup>5</sup>9s<sup>1</sup> vs Mo 4d<sup>5</sup>5s<sup>1</sup>, element 162 7d<sup>7</sup>9s<sup>1</sup> vs Ru 4d<sup>7</sup>5s<sup>1</sup>, element 163 7d<sup>8</sup>9s<sup>1</sup> vs Rh 4d<sup>8</sup>5s<sup>1</sup>, element 164 7d<sup>10</sup>9s<sup>0</sup> vs Pd 4d<sup>10</sup>5s<sup>0</sup>). They thus agree with Fricke et al. on the chemically most analogous groups, but differ from them in that Nefedov et al. actually place elements in the chemically most analogous groups. Rg and Cn are given an asterisk to reflect differing configurations from Au and Hg (in the original publication they are drawn as being displaced in the third dimension). In fact Cn probably has an analogous configuration to Hg, and the difference in configuration between Pt and Ds is not marked.<ref name=nefedov/>
{| class="wikitable" style="text-align: center;"
|+Nefedov et al.'s suggested form (fragment)
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| Cs
| Ba
| La–Lu
| Hf
| Ta
| W
| Re
| Os
| Ir
| Pt
| Au
| Hg
| Tl
| Pb
| Bi
| Po
| At
| Rn
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| Fr
| Ra
| Ac–Lr
| Rf
| Db
| Sg
| Bh
| Hs
| Mt
| Ds
| Rg*
| Cn*
| Nh
| Fl
| Mc
| Lv
| Ts
| Og
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| 119
| 120
| {{nowrap|121–157}}

| 158
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===Pyykkö===
[[Pekka Pyykkö]] used computer modeling to calculate the positions of elements up to ''Z''&nbsp;=&nbsp;172 and their possible chemical properties in an article published in 2011. He reproduced the orbital order of Fricke et al., and proposed a refinement of their table by formally assigning slots to elements 121–164 based on ionic configurations.<ref name="PT172">{{Cite journal|last1=Pyykkö|first1=Pekka|s2cid=31590563|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=161–8|year=2011|pmid=20967377|doi=10.1039/c0cp01575j|bibcode = 2011PCCP...13..161P }}</ref>
[[File:Pyykko periodic table 172.svg|thumb|center|512px]]
In order to bookkeep the electrons, Pyykkö places some elements out of order: thus 139 and 140 are placed in groups 13 and 14 to reflect that the 8p<sub>1/2</sub> shell needs to fill, and he distinguishes separate {{not a typo|5g}}, 8p<sub>1/2</sub>, and 6f series.<ref name=PT172/> Fricke et al. and Nefedov et al. do not attempt to break up these series.<ref name=actrev/><ref name=nefedov/>

===Kulsha===
Computational chemist [[Andrey Kulsha]] has suggested two forms of the extended periodic table up to 172 that build on and refine Nefedov et al.'s versions up to 164 with reference to Pyykkö's calculations.<ref name=primefan/> Based on their likely chemical properties, elements 157–172 are placed by both forms as eighth-period congeners of yttrium through xenon in the fifth period;<ref name=primefan/> this extends Nefedov et al.'s placement of 157–164 under yttrium through palladium,<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=http://www.primefan.ru/stuff/chem/nefedov.pdf}}</ref> and agrees with the chemical analogies given by Fricke et al.<ref name=actrev/>

Kulsha suggested two ways to deal with elements 121–156, that lack precise analogues among earlier elements. In his first form (2011, after Pyykkö's paper was published),<ref name=primefan/> elements 121–138 and 139–156 are placed as two separate rows (together called "ultransition elements"), related by the addition of a 5g<sup>18</sup> subshell into the core, as according to Pyykkö's calculations of oxidation states,<ref name=PT172/> they should, respectively, mimic lanthanides and actinides.<ref name=primefan/><ref name=sicius>{{cite book |last=Sicius |first=Hermann |author-link= |date=2021 |title=Handbuch der chemischen Elemente |language=de |url= |location= |publisher=Springer |page=1085 |isbn= |quote=Kulsha nennt die 36 Elemente zwischen 121 und 156 „Ultransition Elements“ und schlägt vor, sie in zwei Serien aufzuteilen, in eine von 121 bis 138 und eine zweite von 139 bis 156. Die erste ähnelte eher den Lanthanoiden (Seltenerden), die zweite mehr den Actinoiden.}}</ref> In his second suggestion (2016), elements 121–142 form a g-block (as they have 5g activity), while elements 143–156 form an f-block placed under actinium through nobelium.<ref name=dications/>
[[File:Pt172.svg|center|512px|thumb|Kulsha's first suggested form]]
[[File:Pt172expanded.svg|center|1024px|thumb|Kulsha's second suggested form]]
Thus, period 8 emerges with 54 elements, and the next noble element after 118 is 172.<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 |quote=It’s possible that other elements might be synthesized—research is certainly ongoing—but it’s unlikely that the table will ever appear as neat again, since to fill the next row, another fifty-four elements would need to be made.}}</ref>

===Smits et al.===
In 2023 Smits, Düllmann, Indelicato, Nazarewicz, and Schwerdtfeger made another attempt to place elements from 119 to 170 in the periodic table based on their electron configurations. The configurations of a few elements (121–124 and 168) did not allow them to be placed unambiguously. Element 145 appears twice, some places have double occupancy, and others are empty.<ref>{{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 |access-date=}}</ref>

{| class="wikitable"
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| Nd
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| Sm
| Eu
| Gd
| Tb
| Dy
| Ho
| Er
| Tm
| Yb
| Lu
| Hf
| Ta
| W
| Re
| Os
| Ir
| Pt
| Au
| Hg
| Tl
| Pb
| Bi
| Po
| At
| Rn
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| Fr
| Ra
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| Ac
| Th
| Pa
| U
| Np
| Pu
| Am
| Cm
| Bk
| Cf
| Es
| Fm
| Md
| No
| Lr
| Rf
| Db
| Sg
| Bh
| Hs
| Mt
| Ds
| Rg
| Cn
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| Fl
| Mc
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