Fwd: New publisher full-text added to your publication.

[Larry T.]

This is what I received from ResearchGate. Until now that article was obscure and hard to find.

I am including PDF file for those in this PT group who do not have ResearchGate account.

New publisher full-text added to your publication. New publisher full-text added to your publication. ResearchGate and University of California Press have partnered in a program to give researchers new ways of accessing research content. As part of this program, University of California Press has provided a publisher version of one of your articles, which we've added to your publication's page. Using Hund’s Rule and Spin Multiplicity to Assess Competing Versions of Group 3 and f-Block Constituency Article   Full-text available December 2019 The Chemical Educator  Valery Tsimmerman ·  Conal Boyce The article explores Group 3 constituency and f-element representation. In considering those intertwined topics, we frame the discussion in terms of two varieties of periodic table: the one seen in most chemistry texts, where Group 3 is comprised of Sc-Y-La-Ac, and a lesser-known variety, where Group 3 is Sc-Y-Lu-Lr (which makes it akin to Janet’s Left-Step Periodic Table). We also discuss the type seen most often in physics texts, where Group 3 takes the form Sc-Y-*-**, thus footnoting La and Ac to join the other lanthanides/actinides. This variety we look at less closely since it may be regarded as a variant of the first type mentioned. From Hund's rule, spin multiplicity and ground-level microstate data we erect a framework for judging which of the types seems most attuned to atomic structure. Our conclusion is that the type with Sc-Y-Lu-Lr accords best; it possesses an f-block that ends, unequivocally, on the first 4f¹⁴ element (Yb). By contrast, the f-elements of the other two types pass through Yb to halt at the second 4f¹⁴ element (Lu), as if in a delayed reaction or stutter. View full-text This message was sent to val...@perfectperiodictable.com by ResearchGate. To make sure you receive our updates, add ResearchGate to your address book or safe list. See instructions If you don't want to receive these emails from ResearchGate in the future, please unsubscribe. ResearchGate GmbH, Chausseestr. 20, 10115 Berlin, Germany. Imprint. See our Privacy Policy and Terms of Service.

[René]

Thanks Larry. 

It’s mentioned by Google Scholar, too. 

Their entry isn't quite right since it shows nil citations whereas I cited your article in my group 3 FoC article.

I suppose this is timely reminder that we’re due for a periodic discussion on the composition of group 3.

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<Using_Hunds_Rule_and_Spin_Multiplicity_to_Assess_.pdf>

[René]

Larry

It’s interesting that the conclusion of your paper with Conal included the following:

By now, the reader will have noticed that our subtext is: "In a perfect world, we would not be comparing Types A/B/C at all since they would have been long since supplanted by Janet’s LST." Realising how unlikely it is that the LST might rise to such prominence in the foreseeable future, one’s attention turns to Type C as a compromise that might be practical.

[Type A = La in Group 3; Type B = */**; Type C = Lu in Group 3.]

I’ve been reflecting on the use of the term "compromise" in that context. IUPAC has itself explicitly characterised its table (Type B) as a compromise between two established conventions—namely, tables placing either La or Lu in Group 3. In that case, the compromise is between alternatives that already have a more or less comparable standing.

By contrast, framing Type C as a compromise between the conventional medium-long form tables and Janet’s left-step table seems like it’s standing on wobbly ground, since the left-step table lacks a comparable status.

René

On 30 Jan 2026, at 15:20, 'René' via Periodic table mailing list <PT...@googlegroups.com> wrote:

Thanks Larry. 

It’s mentioned by Google Scholar, too. 

To view this discussion visit https://groups.google.com/d/msgid/PT-L/2D5AA03E-BA17-47D0-84F6-460AEC8FCB34%40iinet.net.au.

[Larry T.]

Rene,

We were writing about a compromise between PT that is based on wobbly notion of "behavior" and PT that is based on fundamental property of all observable matter, such as spin.

 Without spin, that is responsible for atoms' electromagnetic interaction, nothing could stand on anything. You would fall through the floor of your home and keep falling through the planet Earth.

  The graphics in that paper clearly demonstrate that ignoring such things as total spin and multiplicity of atoms makes the whole block of the periodic system thrown off the pattern established by three other blocks.

 

  Anyway, thank you for the citation. I hope one day it will be reflected on ResearchGate page.

V.T.

[René]

Hi Larry

Thanks. I think we may be talking past one another slightly, so let me try to restate my point more clearly.

I understand that in your paper with Conal the LST is treated as the fundamental form, and that the Lu table is proposed as a practical compromise between the three chemistry tables (La, Lu, and IUPAC) and the LST, specifically because in the Lu form each block begins with multiplicity 2 and ends with multiplicity 0.

I also agree that, viewed purely in terms of spin multiplicity, the Lu form gives cleaner block starts and ends than the La form, where the f-block begins with multiplicities 1 and 3 and ends with 2 and 2.

My point is spectroscopic rather than philosophical.

Spin multiplicity is only one component of the atomic term symbol. When the full ground-state term symbols (2S+1, L, J) are considered, the Lu form actually introduces one additional mismatch relative to group/block expectations compared with the La form. In other words, Lu–Lr improves multiplicity regularity, but at the cost of overall term-symbol coherence.

So yes, Lu–Lr gives very neat block boundaries in terms of multiplicity, but when term symbols are taken as a whole (which are more encompassing than spin alone), the La–Ac arrangement ends up being slightly more regular.

In addition, the Lu form:

• has one more overall differentiating-electron anomaly than the La form; and
• represents the only case where a pair of elements assigned to the same column have no outer electrons in common with that block (and at its start, at that).

From my perspective, this suggests that the Lu form resolves one aspect of regularity while introducing several new irregularities elsewhere.

René

[Mario Rodriguez]

I want to share a thought while travelling on a bus, especially with René

One problem is actually we don't have a clear definition of what a block is, and there are 2 options:

1. We consider a block is defined by a predominant orbital throughout the period but allowing irregular starts in heavy atoms. The important feature is the overall fit should have the lowest mismatches with theoretical filling. So the f-block can start with La, Ac and Th (despite having d orbital), d-block can start in period 7 with Lr (despite having p orbital), and g-block can start from element 121 (despite also start filling a p orbital, if I remember well the predicted configurations)

2. You consider a block is defined strictly by their valence orbital. In that case, you have to consider La, Ac, and Th (altogether) makes a secondary d-block, Lr makes a secondary p block and after element 120, we wouldn't start the g-block but a kind of tertiary p block. In this case we have to redefine/redraw blocks as they are depicted nowadays.

What we cannot do is making an arbitrary distinction between La and Ac (d1) case compared to Th case (d2), and also Lr (p1) and the start of g-block. Or we assume blocks have irregular starts in heavy atoms or we have to create inserted secondary and even tertiary new blocks. Otherwise it would be an arbitrary distinction between identical situations. In other words, what you consider for La and Ac, you have to consider for Th as well (and the rest). I consider La, Ac and Th are irregular starts of the f-block. Do you consider La, Ac and Th (altogether) should be in the d-block instead? Because it's the only alternative logical option.

Mario Rodríguez Peña

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[Larry T.]

Hi René,

In your last email, you noted:

"Spin multiplicity is only one component of the atomic term symbol. When the full ground-state term symbols (2S+1, L, J) are considered, the Lu form actually introduces one additional mismatch relative to group/block expectations compared with the La form. In other words, Lu–Lr improves multiplicity regularity, but at the cost of overall term-symbol coherence."

Based on this, would you argue for including Sc, Y, La, Ac, and Lu in Group 3 for the sake of "term-symbol coherence"?

Term symbols are only consistent within groups belonging to the s-block and p-block; this "coherence" does not exist within the d-block and f-block groups. Given that, why would Group 3 be granted special status? If you include La and Ac in group 3, the f-block would begin with Ce and Th, creating the similar problem, only in the f-block instead of the d-block. Where is the improvement? If we stick with something as fundamental as electron spin, we can really see how the pattern emerges across all four blocks. 

Best regards,

Larry T.

[René]

On 10 Feb 2026, at 15:18, Larry T. <ora...@gmail.com> wrote:

Hi René,

In your last email, you noted:

"Spin multiplicity is only one component of the atomic term symbol. When the full ground-state term symbols (2S+1, L, J) are considered, the Lu form actually introduces one additional mismatch relative to group/block expectations compared with the La form. In other words, Lu–Lr improves multiplicity regularity, but at the cost of overall term-symbol coherence."

Based on this, would you argue for including Sc, Y, La, Ac, and Lu in Group 3 for the sake of "term-symbol coherence"?

Thanks Larry for your follow-on question.

I wouldn’t argue for Sc, Y, La, Ac and Lu in group 3. While they each have the same term symbol there’s not enough room in group 3 for five metals.

Term symbols are only consistent within groups belonging to the s-block and p-block; this "coherence" does not exist within the d-block and f-block groups.

That’s not quite right. For example, term symbols are consistent for groups 4, 7, 9, 11 and 12 in the d-block.

Given that, why would Group 3 be granted special status? If you include La and Ac in group 3, the f-block would begin with Ce and Th, creating the similar problem, only in the f-block instead of the d-block.

Group 3 doesn’t have any special status.

If La–Ac are included in Group 3, the term-symbol anomalies at the start of the f-block are Ce and Th–Np, and at the end are Lu–Lr, giving a total of seven.

This can be compared to an Lu table in which there is one term-symbol anomaly in the start of the d-block (Lr) and seven anomalies at the start of the f-block (La, Ce, Ac–Np), for a total of eight.

One may further reasonably regard initial term-symbol irregularities as more disruptive to block logic than terminal ones.

Where is the improvement?

There is no term-symbol anomaly in Group 3. There is one less differentiating-electron discrepancy.^ And the f-block does not begin with two elements having no outer electrons in common with that block—a stronger departure from block logic than any comparable irregularity elsewhere in the table.

^ As Eric and Bill Parsons wrote:

“…for the purpose of selecting an optimal periodic table we prefer to consider block membership as a global property in which we focus on the predominant differentiating electron.” (Scerri and Parsons 2018, p. 151).

Scerri ER & Parsons W, What elements belong in Group 3 of the periodic table? In Scerri E & Restrepo G (eds) Mendeleev to Oganesson: A multidisciplinary perspective on the periodic table, pp. 140–151, Oxford University Press, New York (2018)

If we stick with something as fundamental as electron spin, we can really see how the pattern emerges across all four blocks.

I agree about the pattern but it comes at the expense of letting the spin “tail” wag the dog of term symbols, differentiating electrons, and block logic.

While an La table results in a split d-block when presented in 32-column form everyone learns that 4f fills between 5d¹ and 5d². So seeing d¹ → f → d²–d¹⁰ on the table feels natural.

Best regards,

Larry T.

cheers, René

[René]

On 7 Feb 2026, at 01:56, 'Mario Rodriguez' via Periodic table mailing list <PT...@googlegroups.com> wrote:

I want to share a thought while travelling on a bus, especially with René

Thanks very much Mario for contributing your thoughts. It sounds like it was a fairly long bus trip?

One problem is actually we don't have a clear definition of what a block is, and there are 2 options:

1. We consider a block is defined by a predominant orbital throughout the period but allowing irregular starts in heavy atoms. The important feature is the overall fit should have the lowest mismatches with theoretical filling. So the f-block can start with La, Ac and Th (despite having d orbital), d-block can start in period 7 with Lr (despite having p orbital), and g-block can start from element 121 (despite also start filling a p orbital, if I remember well the predicted configurations)

I don’t think the definition of a block is especially problematic. The s-block, for example, is formed due to the differentiating electrons entering an s orbital. Moving to the right we encounter the f-block (disconnected under the main body of the table), the d-block and the p-block.

As Eric and Bill Parsons noted, "...for the purpose of selecting an optimal periodic table we prefer to consider block membership as a global property in which we focus on the predominant differentiating electron.” (Scerri and Parsons 2018, p. 151). As you said, "The important feature is the overall fit should have the lowest mismatches with theoretical filling."

On this basis, an La-Ac Group 3 table is more optimal, because it introduces one fewer differentiating-electron anomaly than an Lu-Lr table.

2. You consider a block is defined strictly by their valence orbital. In that case, you have to consider La, Ac, and Th (altogether) makes a secondary d-block, Lr makes a secondary p block and after element 120, we wouldn't start the g-block but a kind of tertiary p block. In this case we have to redefine/redraw blocks as they are depicted nowadays.

What we cannot do is making an arbitrary distinction between La and Ac (d1) case compared to Th case (d2), and also Lr (p1) and the start of g-block. Or we assume blocks have irregular starts in heavy atoms or we have to create inserted secondary and even tertiary new blocks. Otherwise it would be an arbitrary distinction between identical situations. In other words, what you consider for La and Ac, you have to consider for Th as well (and the rest). I consider La, Ac and Th are irregular starts of the f-block. Do you consider La, Ac and Th (altogether) should be in the d-block instead? Because it's the only alternative logical option.

No arbitrary distinction is being made.

The f-block begins with the first appearance of an f electron at Ce. Thorium with its d- differentiating electron represents an irregular start to the 5f row in the same way that Lr, if placed in group 3, would represent an irregular start to the 5d row.

The situations are not identical however since an La table has one less differentiating electron discrepancy.

In response to your question, there is no need to consider La, Ac and Th (altogether) being in the d-block instead.

Mario Rodríguez Peña

René

[ERIC SCERRI]

Since my work, with my former student Will Parsons, has been mentioned,

The labels of blocks of elements in the periodic table (s,p,d or f) refer to the differentiating electron, not the outermost electron, nor the most energetic electron in any particular atom.

For example, take scandium.  The correct configuration is [Ar] 3d1 4s2.   

The outermost electron is in an s-orbital, and the most energetic electron is also in an s-orbital.  

And yet Sc is classified as being an s-block element because the electron that differentiates it from the previous element, calcium [Ar] 4s2, is that 3d electron.

The only instances where this definition breaks down is with atoms having anomalous configurations.

Consider vanadium.   [Ar] 3d3 4s2 

and chromium            [Ar] 3d5 4s1.  

Here the difference lies both in the d orbital and well as an s orbital.  The notion of differentiating electron becomes ambiguous in all 20 or so anomalous atoms.  But this does not matter, just like the violations of the 

n + l rule don’t matter to the overall architecture of the periodic table.

Chemistry deals with inexact concepts such as the n + l rule, acidity, electronegativity, aromaticity, bonding etc., etc.

This is why I believe that attempts to resolve the group 3 debate, for example, should be decided through broad and general philosophical or conceptual arguments rather than looking at the minutiae of the elements in question, regardless of whether they be chemical, or concerned with spectroscopic term symbols, or what have you.

regards

Eric Scerri

ERIC SCERRI PhD

UCLA

Website: http://www.ericscerri.com
PhilPeople https://philpeople.org/profiles/eric-scerri
Google Scholar https://scholar.google.com/citations?hl=en&user=8w1T5bEAAAAJ
ResearchGate https://www.researchgate.net/profile/Eric-Scerri

Editor-in-Chief of Foundations of Chemistry https://link.springer.com/journal/10698

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