Carlsen (2015)

[Rene]

Here’s a rare example of periodic table that colour codes H (over B) as a metalloid, from https://www.syncopate.us/articles/2007/m28d

I have shown only the p-block, as the full table is 32 rows deep.

I’ve included a consolidated list of grounds for placing H over B.

René

Hydrogen over boron?

There are over a dozen grounds for H over B. I’ve listed them hereafter in no particular order and without judgment as to their strengths, or lack of:

1 to 5

1.    H (Z =1) is half an octet from B (Z =5). As is He (Z = 2) half an octet away from C (Z= 6)

2.    A progression in metallic character, from a weak non-metal (H), through a metalloid (B), via two weaker amphoteric metals (Al-Ga), to two metals (In, Tl)

3.    All elements of the resulting group are capable of forming alloys

4.    On the analogy between B and metals, Greenwood (2001, p. 2057) commented that:

“The extent to which metallic elements mimic boron (in having fewer electrons than orbitals available for bonding) has been a fruitful cohering concept in the development of metalloborane chemistry…Indeed, metals have been referred to as ‘honorary boron atoms’ or even as ‘flexiboron atoms’. The converse of this relationship is clearly also valid…”

5.    H is clearly molecular; B is network covalent (mean coordination number 6.6); Al has interatomic bonding that is partially directional in nature (CN 12); Ga is a molecular metal, having a CN of 7 (i.e. 1+2+2+2); In has a partially distorted structure associated with incompletely ionised atoms and has a coordination number of 4+8; Tl has a close-packed structure (CN 6+6) but an abnormally large inter-atomic distance that has been attributed to partial ionization of the Tl atoms.

6 to 10

6.    H over B yields an honorary metal line (near-metalloids) passing through H-Rn: 

H

B  C

Al Si P

Ga Ge As Se

In Sn Sb Te I

Tl Pb Bi Po At Rn 

H: "Honorary metal in many versions of the activity series" (Chang 1998, p. 151)
C: Lustrous appearance; behaves electrically like a metal (conductivity ~ that of iron at room temperature); band structure of a semi-metal
P: "We have declared phosphorous an honorary metal for the purposes of this monograph…" (Silver and Walden 2012, p. 2)
Se: Lustrous appearance; crystalline structure thought to include weakly "metallic" interchain bonding; counted as a heavy metal
I: "…it is now clear that liquid metal embrittlement (if we may regard iodine as an honorary metal for present purposes…" (Cahn 1992, p. 279)
Rn: Cationic behaviour

Note however that relativistic effects are expected to result in At being a metal rather than a metalloid. 

7.    +1 is known for all members of the resulting hybridized group, H-B-Al-Ga-In-Tl. This oxidation state becomes more stable going from B to Tl such that monovalent Tl is preferred. The halides form B(I) derivatives; B₄Cl₄ is well characterized. In MgB₂ there is a charge of −1 on each B atom. Al(I) chemistry is rare but there is enough of it to support its own Wikipedia article, Aluminium(I). For Ga and In there are e.g. Ga₂Y (Y = O, S, Se); red InCl (mp 225°C), In^I[In^IIITe₂] and In^I[In₃Y₃] (Y=Se, Te)

8.    An extensive chemistry between H and B i.e. the boranes B_xH_y, their anions B_xH_y^–, and related cations e.g. H₂B²⁺ (Miller & Muetterties 1964)

9.    The triangular H₃⁺ cation is the most prevalent form of H in the universe; B can form triangular B₃^2– and B₃⁺ rings 

10. The hydronium cation H₉O₄⁺ and the pentaborane anion B₅H₈⁻ are isoelectronic

11 to 14

11. A resulting diagonal relationship between H and C (Vernon 2020)

12. The dodecaborate ([B₁₂H₁₂]²⁻) ion, image attached, can be "tuned" to give it the properties of many different metals (Lee at al. 2007; University of Missouri-Columbia 2007)

13. Carborane chemistry, BC₂H_n⁺²

14. B in the p-block is analogous to He in the p-block.

Related notes

A.   H over B appears in the literature from as early as 1893 (Rang)

B.   H and has sometimes been placed over B and C (Sanderson 1964) given its electronegativity of 2.2 is between that of boron (2.04) and carbon (2.55)

C.   It's curious to note that if H (2.1 Pauling electronegativity) is placed over B (2.0) and Al (1.5), and if these three are then moved over group 3 as Sc-Y-La-Ac, there is a steady decrease of EN going down group 13, from H to Ac.

D.   The shape of the periodic table with H over B is that of a tower, wall, keep and dungeon (image attached)

References

 Chang RW 1998, Chemistry, 6th ed., McGraw-Hill, Boston

 Greenwood NN 2001, “Main group element chemistry at the millennium”, Journal of the Chemical Society, Dalton Transactions, issue 14, pp. 2055–66

Lee M et al. 2007, “Alkoxy derivatives of dodecaborate: Discrete nanomolecular ions with tunable pseudometallic properties”, Angewandte Chemie International Edition, vol. 46, pp. 3018-3022.

Miller NE & Muetterties EL 1964, “Chemistry of boranes. X.^1,2 borane cations, H₂B(base)₂⁺”, Journal of the American Chemical Society. vol. 86, no. 6, pp. 1033–1038

Rang PJF 1893, The Periodic Arrangement of the Elements, Chemical News, vol. 67, p. 178, https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?PT_id=63

Sanderson RT 1964, A rational periodic table, Journal of Chemical Education, vol. 41, pp. 187–189

Silver S and Walden W (eds) 2012, Metal ions in gene regulation, Springer, Dordrecht

University of Missouri-Columbia 2007, “Discovery of new family of pseudo-metallic chemicals," ScienceDaily, 25 April

Vernon RE 2020, “Organising the metals and nonmetals”, Foundations of Chemistry, vol. 22, pp. 217–233

Useful reading

 Luchinskii GP & Trifonov DN 1981, Some problems of chemical elements classification and the structure of the periodic system, in Uchenie o periodichnosti. Istoriya i sovremennoct’. Nauka, Moscow pp 200–220, in Russian: They discuss four positions proposed for H, i.e. above Li, B, C or F

Attached hereafter is an image of dodecaborate ion, and the shape of the PT with H over B,

[johnmarks9]

All grist to the mill of the wonderful variety of perspectives that the brightest jewel in Indra´s Net provides . . .