Figure 3.12 The revised Scerri left-step Periodic Table (from Ref. [6]).
Commentary
By 2010, the Editor of the Journal of Chemical Education felt that the hydrogen location debate had run its course. In an Editor’s Note, Pienta stated [31]:
… the Journal is implementing a new policy concerning submissions about the periodic table; those that cover new ground will be considered, but continuing arguments on longstanding issues will not be accepted for review.
As the purpose of this book is to look predominantly at the chemical aspects of the Periodic Table, the convention of placing helium as a member of Group 18 will be followed. For hydrogen, it is the Author’s prerogative to choose the location of hydrogen: that will be the Rang, and later Kaesz and Atkins, “lonely” central position.
References
1.D. H. Rouvray, “The Surprising Periodic Table: Ten Remarkable Facts,” Chem. Intell. 3, 39–47 (1996).
2.M. W. Cronyn, “The Proper Place for Hydrogen in the Periodic Table,” J. Chem. Educ. 80, 947–951 (2003).
3.J. W. van Spronsen, The Periodic System of Chemical Elements: A History of the First Hundred Years, Elsevier, Amsterdam, 170 (1969).
4.H. K. Griff, “A Clockwise Spiral System of the Chemical Elements,” J. Chem. Educ. 41, 191 (1964).
5.V. M. Petruševski and J. Cvetković, “On the ‘True Position’ of Hydrogen in the Periodic Table,” Contributions, Sec. Nat. Math. Biotech. Sci. MASA 38(1), 83–90 (2017).
6.E. Scerri, “The Role of Triads in the Evolution of the Periodic Table: Past and Present,” J. Chem. Educ. 85, 585–589 (2008).
7.M. C. Sneed and R. C. Brasted, Comprehensive Inorganic Chemistry, Volume 6: The Alkali Metals; Hydrogen and Its Isotopes, van Nostrand, New York (1965).
8.E. Wigner and H. B. Huntington, “On the Possibility of a Metallic Modification of Hydrogen,” J. Chem. Phys. 3, 764 (1935).
9.A. L. Ruoff et al., “Solid Hydrogen at 342 GPA: No Evidence for an Alkali Metal,” Nature 392, 46–49 (1998).
10.R. P. Dias and I. F. Silvera, “Observation of the Wigner-Huntington Transition to Metallic Hydrogen,” Science 355, 715–718 (2017).
11.J. W. Moore, “Turning the (Periodic) Tables,” J. Chem. Educ. 80, 847 (2003).
12.D. M. Cousins, M. G. Davidson, and D. García-Vivó, “Unprecedented Participation of a Four-Coordinate Hydrogen Atom in the Cubane Core of Lithium and Sodium Phenolates,” Chem. Commun. 49, 11809–11811 (2013).
13.L. J. Sacks, “Concerning the Position of Hydrogen in the Periodic Table,” Found. Chem. 8, 31–35 (2006).
14.G. W. Sears, “A New Form of the Periodic Table as a Practical Means of Correlating the Facts of Chemistry,” J. Chem. Educ. 1(8), 173–177 (1924).
15.R. H. LeRoy, “A Modified Periodic Classification of the Elements Adapted to the Teaching of Elementary Chemistry,” J. Chem. Educ. 8(10), 2052–2056 (1931).
16.H. A. Wagner and H. S. Booth, “A New Periodic Table,” J. Chem. Educ. 22(3), 128–129 (1945).
17.R. L. Rich, “Are Some Elements More Equal than Others?” J. Chem. Educ. 82(12), 1761–1763 (2005).
18.P. J. F. Rang, “The Periodic Arrangement of the Elements,” Chem. News 178 (14 April 1893).
19.R. T. Sanderson, “A Rational Periodic Table,” J. Chem. Educ. 41, 187–189 (1964).
20.R. L. Rich and M. Laing, “Can the Periodic Table Be Improved?” Educ. Química 22, 162–165 (2011).
21.H. Kaesz and P. Atkins, “A Central Position for Hydrogen in the Periodic Table,” Chem. Int. 25(6), 1–2 (2003).
22.E. Scerri, “The Placement of Hydrogen in the Periodic Table,” Chem. Int. 25(7), 1–3 (2003).
23.P. Stewart, “Charles Janet: Unrecognized Genius of the Periodic System,” Found. Chem. 12, 5–15 (2010).
24.M. Laing, “Where to Put Hydrogen in a Periodic Table?” Found. Chem. 9, 127–137 (2007).
25.G. Katz, “The Periodic Table: An Eight Period Table for the 21st Century,” Chem. Educ. 6, 324–332 (2001).
26.E. R. Scerri, “Presenting the Left-Step Periodic Table,” Educ. Chem. 42, 135–136 (2005).
27.H. Bent, New Ideas in Chemistry from Fresh Energy for the Periodic Law, AuthorHouse, Bloomington, Indiana, 117 (2006).
28.O. Novarro, “On the Rightful Place for He within the Periodic Table,” Found. Chem. 10, 3–12 (2008).
29.A. Ramíríez-Solís and O. Novarro, “The First Metals in Mendeleev’s Table: Further Arguments to Place He above Ne and Not above Be,” Found. Chem. 16, 87–91 (2014).
30.W. Grochala, “On the Position of Helium and Neon in the Periodic Table of Elements,” Found. Chem. 20, 191–207 (2018).
31.N. J. Pienta, “Editor’s Note,” J. Chem. Educ. 87, 783 (2010).
Chapter 4
The Group 3 Problem
In Chapter 3, the controversy around the placement of hydrogen (and, to a lesser extent, helium) was described. There is another controversial topic — more so, in fact — of the element choices for the two lower members of Group 3. Here, the issues will be described.
Even more contentious than the placement of hydrogen has been the membership of Group 3. The first two members are self-evident: scandium and yttrium. But which are the subsequent members of the Group? Using the long (32-column) form of the Periodic Table, there is no issue: lutetium and lawrencium fall naturally in place.
However, the 18-column form of the Periodic Table is ubiquitous. The issue becomes which set of 14 elements are pulled out and placed beneath, or whether all 15 elements are placed beneath. Is it the electron configuration or chemistry which should determine which elements occupy these positions? The debate revolved around the third member of the Group: lanthanum or lutetium, as actinium and lawrencium are highly radioactive (hence with short half-lives) and with little established chemistry. In fact, lawrencium was unknown at the time of the early discourse and actinium was assumed to be a transition metal (see Chapter 13) [1].
A History of the Debate
Jensen provided a comprehensive review of the early history of the discourse [2]. In the 1920s and 1930s, lutetium was assigned to Group 3. It was only in the 1940s that the Periodic Table was restructured according to electron configurations. At this time, lanthanum was considered to be the “legal” occupant of the “box” for Period 6, Group 3. Using arguments that will be introduced later, Jensen took the position first proposed by Luder in 1970 [3] that the correct occupants were lutetium and lawrencium, deposing lanthanum and actinium, that were sent to the rows below in the 18-group Periodic Table.
Clark and White reviewed the type of Periodic Table utilized in common U.S. textbooks over the time frame of 1948 to 2008 [4]. They identified, and provided abbreviations for, the three different 18-column Periodic Table formats (displayed in Figure 4.1).
•14CeTh. Lanthanum and actinium are placed in Group 3; the 14-member “boxes” commence with cerium (lanthanoids) and thorium (actinoids).
•14LaAc. Lutetium and lawrencium are placed in Group 3; the 14-member “boxes” commence with lanthanum (lanthanoids) and actinium (actinoids).
•15LaAc. The places in Group 3 are left vacant; the 15-member “boxes” commence with lanthanum and end with lutetium (lanthanoids), then commence with actinium and end with lawrencium (actinoids).
Clark and White showed that from 1948 up until 1984, textbooks were about evenly split between the 15LaAc and 14CeTh formats. It seems to have been Jensen’s 1982 article that led to the appearance of, and growth in, the 14LaAc format to the point where it was about an even split between 14CeTh and 14LaAc, the 15LaAc disappearing.
Figure 4.1 The three options for the members of Group 3.
At times, it has seemed less a dispute and more a case of confusion, as Jensen pointed out in 2008 [5]. He noted that the text Advanced Inorganic Chemistry by Cotton and Wilkinson used the 14CeTh format on the back flyleaf, but the 15LaAc within the text. Jensen also reported that conversely, Housecroft and Sharpe in the text Inorganic Chemistry, used the 15LaAc format
on the front flyleaf but the 14CeTh format within the text.
The Dispute Becomes Heated
The years of 2008 and 2009 were busy ones for this debate. In later 2008, Lavelle came to the defense of the former arrangement, arguing that lanthanum and actinium were indeed members of the d-block elements and should remain in the body of the Periodic Table [6].
In a subsequent letter to the Journal of Chemical Education, Lavelle referred to the article by Clark and White [7]:
In their letter Clark and White wonder why the chemistry education community has not uniformly adopted just one form of the periodic table. Part of the answer is that the majority who are silent on this issue do not want to be attacked by the vocal proponents who insist that lanthanum and actinium must be in the f-block and lutetium and lawrencium must be in the d-block…. I do not wish to enter into conflict but hopefully my article gives voice to those who have been silent. Perhaps our university chemistry textbooks should include brief mention of the difficulties on having one form of the periodic table.
Clark responded, making the point raised by this Author at the beginning of the chapter. The discourse was based upon the defect of the 18-column form of the Periodic Table, necessitating 14 elements to be ripped from their rightful place and “dumped” beneath [8]:
… I now favor relegating the flyleaf [18-column] forms to history and shifting the resulting debate to which of the long-form tables is best. There will still be arguments as to which long-form table to use, but these will be healthier arguments than the electron shift agonies of past decades.
The feud continued into 2009. Jensen replied to Lavelle’s article [9]:
For obvious reasons I feel compelled to comment on the recent commentary by Lavelle on the placement of La and Ac in the periodic table as I feel that it is not only based on inconsistent reasoning but also contains a serious distortion of the contents of my original article dealing with the subject.
In the same rebuttal, Jensen concluded with [9]:
Finally, with regard to Lavelle’s assertion that in his accompanying letter that he speaks for the silent majority who have been cowed into submission by the vocal proponents of the Lu-Lr alternative, I can only say that discussion of this subject is welcome, but for such discussion to be profitable it must be both logically consistent and relevant.
Lavelle’s response was published on the following page. He reiterated that, in his view, Jensen’s assignments were only accepted by a minority. Lavelle continued [10]:
The point of my discussion on lawrencium was that those who insist on placing lutetium and lawrencium in the d-block, and insist that others do also, are selective in the literature they cite to support the claim.
The personal enmity came through in the closing sentence [10]:
Jensen appears to be unaware of the self-righteous content of some of his articles in this Journal that detract from his otherwise many historically informative publications.
Laing intervened. Jensen, in his 2008 contribution to the debate [5], had cited the Periodic Table from Ephraim’s textbook Periodisches System der Elements. Laing pointed out that in the 6th English translation, Fritz Ephraim’s Inorganic Chemistry [11], the lanthanoids were displayed differently. He added [12]:
In the 25 years that passed between editions, the La-Lu problem was no closer to solution. Another 55 years have now gone by and the debate rages on: plus ça change, plus c’est la même chose…. Arguing about the “right place” for thorium and uranium (or La and Lu or Ac and Lr) in a f- or d-series seems purposeless. Why “should” thorium, [Rn]6d27s2, be best placed in the f-block? … there is no ideal or perfect periodic table.
Then Scerri joined the debate. In his commentary, he reiterated the point by Clark (and by this Author) [13]:
It is generally agreed that the conventional or medium-long form table [that is, s-d-p, more often called the short form] continues to survive only because it is more conveniently reproduced in textbooks and wall-charts than the long-form table. The medium-long form table [18-column] relegates as many as 28 elements to a kind of disconnected footnote, and thereby allows one to keep the periodic table relatively slim and having 18 columns. The long-form table, which some textbooks feature, consists of a width of 32 columns. But on the plus side it includes the lanthanoids and actinoids in their rightful place within the main body of the table. More importantly perhaps, it maintains an uninterrupted and increasing sequence of atomic number.
The exchanges ceased, though whether it was because exhaustion had set in, or because the Journal of Chemical Education had decided to bar any future acrimonious exchanges (as with the hydrogen placement issue — see Chapter 3), it is not known.
IUPAC Becomes Involved
It was in 2009 that Leigh felt it necessary to clarify the position of the International Union of Pure and Applied Chemistry (IUPAC) on the various periodic table designs in the pages of Chemistry International [14]:
In fact, IUPAC has not approved any specific form of the periodic table, and an IUPAC-approved form does not exist, though even members of IUPAC themselves have published diagrams titled “IUPAC Periodic Table of the Elements.”
Leigh briefly mentioned the Group 3 issue [14]:
As the long form [18-column] places them, the lanthanoids and actinoids sit rather uncomfortably each in a single place, but should lanthanum and actinium be grouped directly with their congeners?
He, too, alluded to the fact that, with what he called the long–long form (here called simply the 32-column form) the Group 3 placement issue did not arise.
Citing Leigh, Scerri argued that IUPAC did need to take a stand on the Group 3 issue [15]:
I propose that IUPAC should in fact take a stance on the membership of particular groups even if this has not been the practice up to this point.
As some 18-member Periodic Tables showed Group 3 as Sc–Y–La–Ac and others Sc–Y–Lu–Lr, Scerri felt the issue needed to be definitively resolved [15]:
This has led to a situation in which chemistry students and professionals alike are often confused as to which version is “more correct” if any.
Scerri pointed out that if the long form of the Periodic Table was written out, then keeping the f- and d-blocks intact, lutetium and lawrencium would naturally occur beneath scandium and yttrium. The Sc–Y–La–Ac alternative could only be structured if, in the long form, the d-block elements of Group 3 (scandium and yttrium) were shifted over next to Group 2, breaking up the transition metal series.
Jensen then rejoined the debate, repeating his 1982 position that lutetium and lawrencium should be assigned to the d-block and lanthanum and actinium as the first members of the f-block. At the end of the abstract, he could not resist the opportunity to continue the feud [16]:
This update is embedded within a detailed analysis of Lavelle’s abortive 2008 attempt to discredit this suggestion.
In 2016, an IUPAC task force was instituted to endeavor to resolve definitively which option would be given official IUPAC status [17]. Toward this endeavor, Scerri and Parsons have compiled their own account and recommendations [18].
Some Aspects of the Group 3 Debate
The complexities of the debate would fill a volume on its own. Only some of the key issues will be addressed here. It was unfortunate that the first modern contribution to the discourse, that by Luder, was published in the obscure and long-deceased journal, Canadian Chemical Education [3]. In the article, he used two (innovative) 32-column Periodic Tables to show that, by placing lanthanum and actinium in Group 3, Group 3 then became separated from the d-block elements. Instead, it was isolated next to the Group 2 elements. On the other hand, placing lutetium (lawrencium being then unknown) as the third member of Group 3, ensured that these elements became placed next to Group 4. Luder considered the second option the only logical placement. The two options are shown in Figure 4.2.
Physical Properties as Criteria for Location
Jensen’s 1982 article [2] raised some i
nteresting points about chemical compatibility. Three of the criteria he chose were atomic radii, the sum of the first two ionization energies, and the melting point. He compared the two options of Sc–Y–La and Sc–Y–Lu with the subsequent d-block sequences of Ti–Zr–Hf, V–Nb–Ta, and Cr–Mo–W (Figure 4.3).
In terms of atomic radii, the early transition metals show a systematic pattern of an increase from 4th Period to 5th Period, then a decrease to the 6th Period. This decrease is a result of the so-called “lanthanoid contraction” (see Chapter 12). The Sc–Y–Lu series follows this pattern, while the atomic radius of lanthanum is larger than that of yttrium. There is an inverse pattern with the sum of the first two ionization potentials, but then this would be related to atomic radius and is not surprising. For the melting point, the trend is not so precise, though the Sc–Y–Lu series does show an increase (as do the transition metals), while the Sc–Y–La series shows a decrease. From these data, Jensen noted that scandium and yttrium better matched with lutetium. Hence Group 3 was better considered as Sc–Y–Lu–Lr.
Figure 4.2 The two possible locations for Group 3 according to Luder (Ref. [3]).
In addition to the numerical data, Jensen provided some comparative properties, three of which are shown in Table 4.1. A large range of properties are common to all rare earth elements, but Jensen found a few specific examples where the properties of lanthanum differed from those of scandium, yttrium, and lutetium. Again, he concluded that the better fit was Sc–Y–Lu–Lr.
Figure 4.3 Diagrams comparing properties of Group 3 “candidates” to those of early transition metals (adapted from Ref. [2]).
Table 4.1 Some comparative properties of scandium and yttrium with lanthanum and lutetium (adapted from Ref. [1])
Periodic Table, The: Past, Present, And Future Page 6