Internet Database of Periodic Tables
There are thousands of periodic tables in web space, but there is only one comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Dr Mark R Leach.
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LeRoy's Periodic Table
R.H. LeRoy, Teaching the Periodic Classification of Elements, School Science and Mathematics 1927, 27: 793-799. This formulation thulium in group IC and has the actinides in the C groups, analogous to the lanthanides, two decades before Seaborg.
"This 1927 formulation has several remarkable features.
"The lighter and heavier lanthanides and actinides are shown in numbered C groups i.e. C4, C5, C6, C7 and C1, C2, and C3. The 14 remaining elements between C7 and C1 are labelled as transition elements, analogous to the old chemistry notion of the ferromagnetic and platinum metals in IUPAC groups 9 to 11 being labelled as transition elements. There is no known Tm(I) although this would not be inconceivable. Nd is in group C6, which doesn't quite work since there is no Nd(VI) although such an oxidation state is not inconceivable given the existence of Pr(V). in group C7, Pm(VII) is not known. For the actinides, Md(I) has been reported but not confirmed.
"B-Al-Sc-Y-La-Ac are shown as main group metals; that would be consistent with their chemistry. While Sc-Y-La-Ac are routinely classified as transition metals their chemistry is largely that which would be expected of main group metals following the alkaline earths in IUPAC group 2.
"The author refers to the noble gases as 'transitional'. The noble gases bridge the most reactive groups of elements in the periodic table – the alkali metals in group I and the halogens in group VII. That's a concept that's rarely referred to these days even though it's still quite valid.
Ga-In-Tl are shown as B3 metals, falling just after Zn-Cd-Hg in group B2, and Cu-Ag-Au in group B1. That doesn't work for Ga etc, which are nowadays regarded as main group metals.
"H is shown floating above the A elements, and in the transitional zone, with links to F and to Li."
Thanks to John Marks for the tip, and to René for the comments/analysis!
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