Editing Periodic table (section)

== Alternative periodic tables ==
{{Main|Types of periodic tables}}
[[File:Elementspiral (polyatomic).svg|thumb|350px|[[Otto Theodor Benfey]]'s spiral periodic table (1964)]]

The periodic law may be represented in multiple ways, of which the standard periodic table is only one.<ref>Scerri, p. 20</ref> Within 100 years of the appearance of Mendeleev's table in 1869, [[Edward G. Mazurs]] had collected an estimated 700 different published versions of the periodic table.<ref name="Jensen">{{cite journal|last1=Jensen|first1=William B. |date=January–April 1986 |title=Classification, symmetry and the periodic table|journal=Comp. & Maths. With Appls.|volume=12 |issue=1–2 Part B|pages=487–510 |url=https://dx.doi.org/10.1016/0898-1221%2886%2990167-7 |access-date=18 January 2017|archive-url=https://web.archive.org/web/20170131184706/https://www.che.uc.edu/Jensen/W.%20B.%20Jensen/Reprints/028.%20Periodic%20Table.pdf |archive-date=31 January 2017 |url-status=live |doi=10.1016/0898-1221(86)90167-7}}</ref><ref name="Papers">{{Cite book |url=https://othmerlib.sciencehistory.org/record=b1069103~S6 |title=Edward G. Mazurs Collection of Periodic Systems Images |publisher=[[Science History Institute]] |type=Finding Aid |access-date=2 October 2018 |archive-url=https://web.archive.org/web/20190327082328/https://othmerlib.sciencehistory.org/record%3Db1069103~S6 |archive-date=27 March 2019 |url-status=live}} Click on 'Finding Aid' to go to full finding aid.</ref> Many forms retain the rectangular structure, including [[Charles Janet]]'s left-step periodic table (pictured below), and the modernised form of Mendeleev's original 8-column layout that is still common in Russia. Other periodic table formats have been shaped much more exotically, such as spirals ([[Otto Theodor Benfey]]'s pictured to the right), circles and triangles.<ref>{{cite journal |last=Francl |first=M. |title=Table manners |journal=Nature Chemistry |volume=1 |date=May 2009 |pages=97–98 |url=https://ericscerri.com/Michelle-Nat%20Chem.pdf |bibcode=2009NatCh...1...97F |doi=10.1038/nchem.183 |issue=2 |pmid=21378810 |url-status=live |archive-url=https://web.archive.org/web/20121025135145/https://ericscerri.com/Michelle-Nat%20Chem.pdf |archive-date=25 October 2012}}</ref>

Alternative periodic tables are often developed to highlight or emphasize chemical or physical properties of the elements that are not as apparent in traditional periodic tables, with different ones skewed more towards emphasizing chemistry or physics at either end.<ref name="Scerri402">Scerri, pp. 402–3</ref> The standard form, which remains by far the most common, is somewhere in the middle.<ref name="Scerri402" />

The many different forms of the periodic table have prompted the questions of whether there is an optimal or definitive form of the periodic table, and if so, what it might be. There are no current consensus answers to either question.<ref name="sesqui">{{cite web
 |url=https://blog.oup.com/2019/01/happy-sesquicentennial-periodic-table-elements/
 |title=Happy sesquicentennial to the periodic table of the elements
 |last=Scerri
 |first=Eric
 |date=29 January 2019
|publisher=Oxford University Press
 |access-date=12 April 2019
|archive-url=https://web.archive.org/web/20190327082337/https://blog.oup.com/2019/01/happy-sesquicentennial-periodic-table-elements/
 |archive-date=27 March 2019
|url-status=live
 }}</ref><ref name="Scerri402" /> Janet's left-step table is being increasingly discussed as a candidate for being the optimal or most fundamental form; Scerri has written in support of it, as it clarifies helium's nature as an s-block element, increases regularity by having all period lengths repeated, faithfully follows Madelung's rule by making each period correspond to one value of {{mvar|n}} + {{math|ℓ}},{{efn|name=lowdin|Authors differ on whether the {{mvar|n}} + {{math|ℓ}} rule has yet been derived from quantum mechanics. Scerri claims that it has not,<ref>Scerri, p. 255</ref><ref>{{cite book |last=Scerri |first=ER |date=2021 |editor-last1=Giunta |editor-first1=CJ |editor-last2=Mainz |editor-first2=VV |editor-last3=Girolami |editor-first3=GS |title=150 Years of the Periodic Table: Perspectives on the History of Chemistry|publisher=Book Publishers |pages=409–423 (414) |chapter=The Impact of Twentieth-Century Physics on the Periodic Table and Some Remaining Questions in the Twenty-First Century |doi=10.1007/978-3-030-67910-1_16|isbn=978-3-030-67909-5 }}</ref> despite several attempts to do so.<ref>{{Multiref2
|1={{cite journal |last1=Scerri |first1=ER |date=2009 |title=The dual sense of the term 'element', attempts to derive the Madelung rule and the optimal form of the periodic table, if any|url= |journal=Int J Quantum Chem |volume=109 |issue= 5|pages=959–971 |doi=10.1002/qua.21914 |bibcode=2009IJQC..109..959S |access-date=}}
|2={{cite journal |last1=Bent |first1=HA |last2= Weinhold|first2=F |date=2007 |title=News from the periodic table: an introduction to periodicity symbols, tables and models for higher order valency and donor-acceptor kinships|url= |journal=J Chem Educ |volume=84 |issue= |pages=1145–1146 |doi=10.1021/ed084p1145 |access-date=}}
|3={{cite journal |last1=Allen |first1=LC |last2=Knight |first2=ET |date=2002 |title=The Löwdin challenge: origin of the (Madelung) rule for filling the orbital configurations of the periodic table|url= |journal=J Quantum Chem |volume=90 |issue= |pages=80–82 |doi= 10.1002/qua.965|access-date=}}
|4={{cite journal |last1=Wong |first1=DP |date=1979 |title=Theoretical justification of Madelung's rule|url= |journal= J Chem Educ |volume=56 |issue= 11|pages=714–717 |doi=10.1021/ed056p714 |bibcode=1979JChEd..56..714W |access-date=}}
|5={{cite journal |last1=Demkov |first1=YN |last2=Ostrovsky |first2=V |date= 1972|title=n + ' filling rule in the periodic system and focusing potentials.|url= http://www.jetp.ras.ru/cgi-bin/dn/e_035_01_0066.pdf|journal=Soviet Physics JETP |volume=35 |issue= |pages=66–69 |doi= |access-date=8 February 2024}}}}</ref> On the other hand, Ostrovsky, who has claimed such justification from 1971, wrote "Some authors insist that 'still nobody has deduced the n+l rule from the principles of quantum 
mechanics', while others present quantum justification of the rule that was not ever disputed."<ref>{{cite journal |last1=Ostrovsky |first1=V. N. |date=2005 |title=On Recent Discussion Concerning Quantum Justification of the Periodic Table of the Elements |url= |journal=Foundations of Chemistry |volume=7 |issue=3 |pages=235–239 |doi=10.1007/s10698-005-2141-y |s2cid=93589189 |access-date=}}</ref> Other authors argue that such a derivation is not necessary, because it admits exceptions.<ref>{{cite journal |last1=Scerri |first1=Eric |date=2012 |title=What is an element? What is the periodic table? And what does quantum mechanics contribute to the question? |url=https://philpapers.org/archive/SCEWIA.pdf |journal=Foundations of Chemistry |volume=14 |issue= |pages=69–81 |doi=10.1007/s10698-011-9124-y |s2cid=254503469}}</ref>}} and regularises atomic number triads and the first-row anomaly trend. While he notes that its placement of helium atop the alkaline earth metals can be seen a disadvantage from a chemical perspective, he counters this by appealing to the first-row anomaly, pointing out that the periodic table "fundamentally reduces to quantum mechanics", and that it is concerned with "abstract elements" and hence atomic properties rather than macroscopic properties.<ref>{{cite journal |last1=Scerri |first1=Eric |date=2021 |title=Various forms of the periodic table including the left-step table, the regularization of atomic number triads and first-member anomalies |url= |journal=ChemTexts |volume=8 |issue=6 |pages= |doi=10.1007/s40828-021-00157-8 |s2cid=245540088 }}</ref>
{{Clear|right}}
{{Periodic table (left step)}}