Magnum Prediction Chart
Jeana Rodia
It would be useful if the discussion could be condensed but not frozen into an intermediate StateOfMatter overview: those points, arguments, results that should be kept and reused. Gaseous parts can be let go. When we do nothing, all will be lost and no consequences can be implemented.
I have decided to terminate my participation in the main thread, as I will lack the time for it from tomorrow and there is no point in repeating myself more than I already have been doing. I will only fill in responses in my column 4 here, if Sandbh adds anything else to column 3. Double sharp (talk) 06:41, 5 April 2020 (UTC)
DS notes that this suggests an analogy to why Sc-Y-La has often passed without comment: Y3+ and La3+ both have noble gas configurations, which grants them some second-order similarities, whereas Lu3+ does not. The fact, however, that this argument is not used to make group 3 start B-Al-Sc, or group 4 go C-Si-Ti-Zr-Ce-Th, suggests to him that more important considerations are at play for element placement.
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4Droog Andrey, a computational chemist, offered as an example that for Ni complexes, only 1s, 2s, and 2p could be ignored as core electrons without significant consequences: in other words, at least the outermost core orbitals must be included, but that doesn't make them have significant valence involvement. A similar situation happens for the inclusion of d orbitals for hypervalent compounds, see Errol G. Lewars' Modeling Marvels (p. 59): "Including d functions in a basis set for calculations on hypercoordinate compounds may improve the accuracy of the results (this can easily be tested by comparison with known molecules), but this does not mean that physical d orbitals (whatever that may mean) are involved: the orbitals may merely be acting as polarization functions, skewing the s and p orbitals in more propitious directions".
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5 Take basicity of oxidation states for an example: witness how the maximum basic oxidation state moves from +1 in period 2, to +2 in period 3, to +3 in periods 4 through 6, to +5 in period 7, rather than having a group divide. One can see similar trends for example in the structures and degree of hydrolysis of chlorides in water, in which group divides are also absent. The appearance of a "group divide" in the specific situation when only d-block group oxidation states are considered stems from a coincidence in the d block only: the increased size going from 3d to 4d is partially counteracted by the fact that the EN doesn't go down very much (in fact it sometimes goes up), and there is no increased size going from 4d to 5d because of the Ln contraction (this added to an increase in electronegativity). Therefore, generalised Fajans' rules (acidity increases as electronegativity and charge increase and atomic radius decreases) predict that the group divide from 3d to 6d will move really slowly, as it in fact does: Sc3+ is amphoteric, its heavier congeners are basic; but the first basic group 4 cation is Rf4+. Once we get the EN drop and size increase back, we can go up to fantastic heights: Th4+ and Pa5+ are basic cations, as their EN is lower and their size is greater. And once the charge stops increasing, the group divide disappears: compare Sc3+, Ti3+, V3+, and we can see there isn't a significant difference (all three form chlorides that dissolve in water rather than hydrolyse, whereas the chlorides of Ti4+ and V4+ hydrolyse). And once we bring the size down to a minimum, we see already that BeCl2 and BCl3 are hydrolysing in water, even coming before the +3 vs +4 line, and the only reason CCl4 is spared that fate is steric hindrance.
Rather than dwelling upon the minutiae of the individual properties of La and Lu, I attempted to take more of a helicopter view. That meant examining the group in the context of its surrounds; the congruity of the f-block; patterns seen elsewhere in the periodic table; the periodic law; and global considerations. Along the way I entertained a few more detailed (ancillary) arguments where I felt these were required to provide context, were novel, or provide useful insights.
From a Platonic symmetry perspective and perhaps that of physics, and on some grounds of regularity but not on others, it can be argued that Lu is better placed under Y. But not from a chemistry perspective, or at least not as well.
Shall we observe ScCl3 vs TiCl4, call it a fundamental group 3-4 divide, ignoring its disappearance for ScCl3 vs TiCl3, shifting past the +4 state in the 5f row, and before the +2 state for periods 2 and 3?
No! An end to "one argument here, one argument there, never the twain shall meet". Foundational periodicity must know no boundaries. Shall we be denied following Mendeleev, projecting into the unknown, where no boundaries are charted? Shall we holistically seek working generalisations, or argument barrages at each other's throats within milliseconds without artificial leashes?
Ever-reliable electronic structure, that solved formerly unsolvable Be-Mg-Zn and B-Al-Sc, truly is the "helicopter view": logically deriving continuous trends from theory, without artificial divides. The PT's rich structure is only derivable from holistic criteria. Locality is the next level!
Shall we endlessly copy mistakes of a century ago, when electron filling wasn't understood, and 4f was a one-off interruption of the d block? Emphasise the ground-state delayed start of 4f/5f forever, when it means nothing for chemistry, their ends still happen at Yb/No, blinding ourselves to the reproachful counterexamples of thorium and the looming 8th row?
Or shall we progress and heed luminaries: Seaborg, Jensen, Schwarz, Wulfsberg, and Jrgensen, who long ago exposed the hollowness of ground-state DEs? Shall we deny the crown of useful generalisations to ideal configurations, given willingly to ideal gases, crystals, and solutions?
I still don't see a single La argument with a leg to stand on. Especially the point about sources who really consider the question mostly plumping for Lu tells me that an RFC is the right way to go here to correct the group 3 situation. (We can correct the group 2 situation and move helium there once we get the critical mass: right now I think we are in the equivalent situation as Jensen writing in 1982, with the advocacy of Grochala, Grandinetti, and the late Henry Bent.) Points 15 and 20 (in the right-hand column) are why I think an RFC is justified. Double sharp (talk) 16:47, 3 April 2020 (UTC)
As for how much of this is still active: mostly just the bottom of it at this point, from "Falsifiability" onwards, I guess. (I've just archived another big chunk into archive 42, which is now 1.3M...) Since Sandbh has recently stated that he won't address old ground, and the old ground is the key to our being in disagreement, I am not sure if there is anything new left that we need to finish addressing. I am also not sure how much inviting outsiders will help, because frankly the material required to tackle this subject is rather specialised, and unless your focus is rare earth chemistry (so these elements are the relevant ones, and even then it may not work so well because intraperiod resemblances must also be brought in) or the foundational aspects of general inorganic chemistry (i.e. regularities across the whole table, not just one region of it), it probably doesn't matter much to you. If we bring in an outsider, it should be one whose expertise is on one of these chemical branches.
So probably in the future an RFC should start, except that by mid-April I shall be a lot busier and therefore maybe the great big 2nd RFC to fix group 3 will have to be delayed until July. So perhaps what we should do is:
I still would like to thank Sandbh for the discussion, since it has definitely sharpened and greatly improved my approach to the periodic table. I still disagree with him, of course. ^_^ And I would also like to thank Droog Andrey for initially showing me the more advanced chemistry required to understand why the La table must be rejected. And also R8R, Dreigorich, and all other present and past participants in the group 3 debate, ranging all the way back those we cite who published about this in the last century. Double sharp (talk) 02:23, 3 April 2020 (UTC)
Double sharp and I have provided an overview of the group 3 situation in a Background section (18 numbered bullets), a Current state of affairs section (39 numbered bullets), and closing statements (400 words each).
You compare Eu and Yb with Cr and Cu, but that's just ridiculous. Look at the densities, phase transition temperatures, standard potentials, electronegativity, etc. along the atomic number, and you will see that. Actually neither Eu/Yb, nor Gd/Lu are "anomalous", the trends are smooth along the whole subfamilies La-Eu and Gd-Yb without any jumps, that's clearly seen from my chart.
Suppose we decided to start every period with group 2 element and end it with group 1 element. Your arguments will stand in that situation. Well, the periodicity is still here. The extreme properties of the penultimate elements of each period are just because of the filled p6 configuration, like d10 in Cu and Ag. All is clear, isn't it? ...
Again, the trends Sc-Y-La-Ac or Sc-Y-Lu-Lr are not at all about the configurations of neutral atoms, no matter gas phase or metal phase (BTW, there's no any physical sense in atomic configuration in condensed phase, because there's no pure atoms and no atomic wavefunctions). The trends are about real compounds and their properties. Boiling point trend of lanthanides definitely supports Sc-Y-Lu-Lr since it supports natural subfamilies La-Eu and Gd-Yb.
A few people (not necessarily in this forum) feel that I sound like an old cloistered cleric, quoting chapter and verse, in order to defend the established tradition. In fact people familiar with me and my work know I can come up with, and promote, some far out ideas. So my support for La has nothing to do with defending the faith, so to speak.
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