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Year: 2020

PT id = 1174, Type = formulation

Split s-, p- & d-Block Periodic Table

René Vernon presents a periodic table formulation with split s-, p- & d-blocks.

The traditional form of periodic table is a hybrid of an electronic and a chemistry based table.
An electronic or physics-based table would show (a) He over Be; and (b) group 3 as Sc-Y-Lu-Lr; and (c) group 13 as B-Al-Ga-In-Tl
A chemistry-based table would show (d) He over Ne; and (e) B-Al over Sc-Y-La-Ac.
What we have instead is a hybrid table with 1(c) and 2(d). It is not as symmetric or tidy as the pure Lu form; neither is it as irregular as the form with three split blocks.

The details: Group 3 as B-Al-Ga-In-Tl

Al over Sc has some history, which seems to have been forgotten.

Here are some other tables with B-Al-Sc-Y-La:

Rang (1893)
Gooch & Walker (1905)
Cuthbertson & Metcalfe (1907)
Baur (1911)
Rydberg (1913)
Black & Conant (1920)
Lewis (1923)
Hubbard (1924)
Deming's table (1925), which popularised the medium-long form
Antropoff (1926)
LeRoy's table (1927)
Irwin (1939)
Seaborg (1945), with B left in group 13
Yost & Russell (1946)
Coryell (1952)
Pauling's table (1960)
Habishi's Metallurgist's Periodic Table (1992), Habishi leaves B in group 13

What was it that these luminaries knew about B-Al-Sc-Y-La-Ac that is deemed to be no longer relevant, and why is that the case?

Deming (1947, Fundamental Chemistry, 2nd ed. p. 617) located Al with the pre-transition metals in groups 1?2. Cox (2004, Inorganic Chemistry, 2nd ed. p. 185) refers to the pre-transition metals as those in groups 1 and 2, and Al. Here's that 2019 periodic table (by me), recording oxidation number trends, further suggesting B and Al are better placed over Sc.

In this vein, Rayner-Canham (2020, The periodic table: Past, present, and future, pp. 178–181) writes:

"It was Rang in 1893 who seems to have been the first, on the basis of chemical similarity, to place boron and aluminum in Group 3.

"Such an assignment seems to have been forgotten until more recent times. Greenwood and Earnshaw have discussed the way in which aluminum can be considered as belonging to Group 3 as much as to Group 13 particularly in its physical properties. Habashi has suggested that there are so many similarities between aluminum and scandium that aluminum's place in the Periodic Table should actually be shifted to Group 3.

"In terms of the electron configuration of the tripositive ions, one would indeed expect that Al³⁺ (electron configuration, [Ne]) would resemble Sc³⁺ (electron configuration, [Ar]) more than Ga³⁺ (electron configuration, [Ar]3d10). Also of note, the standard reduction potential for aluminum fits better with those of the Group 3 elements than the Group 13 elements (Table 9.2) – as does its melting point.

"In terms of their comparative solution behavior, aluminum resembles both scandium(III) and gallium(III). For each ion, the free hydrated cation exists only in acidic solution. On addition of hydroxide ion to the respective cation, the hydroxides are produced as gelatinous precipitates. Each of the hydroxides redissolve in excess base to give an anionic hydroxo-complex, [M(OH)₄]^–... There does seem to be a triangular relationship between these three elements. However, aluminum does more closely resemble scandium rather than gallium in its chemistry. If hydrogen sulfide is bubbled through a solution of the respective cation, scandium ion gives a precipitate of scandium hydroxide, and aluminum ion gives a corresponding precipitate of aluminum hydroxide. By contrast, gallium ion gives a precipitate of gallium(III) sulfide. Also, scandium and aluminum both form carbides, while gallium does not."

To answer my own question as to why group 3 as B-Al-Sc-Y-La-Ac has been forgotten.

I suspect what happened is that it was historically known that group 3 was better represented as B-Al-Sc-Y-La-[Ac]. Then, with the advent and rise of modern electronic structure theory, B-Al- got moved to the p-block because, after all, they were p-block elements, never mind the damned chemistry. And La stayed in the d-block since it was the first element to show 5d electron, and 4f did not show until Ce. And Lu stayed where it was since even thought it was learnt that the f shell become full at Yb, rather than Lu, nothing changed about the chemistry of Lu. Nowadays, this has all been forgotten.

The modern periodic table is a chemistry-physics hybrid.

Lu in group 3 demands He over Be. La in group 3 demands B-Al over Sc. Neither option gets up. The more important consideration is to teach the history and have students and chemists appreciate both perspectives.

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