The INTERNET Database of Periodic Tables
There are hundreds 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.
Hackh's Periodic Spiral
From a Scientific American in March 1919, an article by Ingo W. D. Hackh discussing the classification of the elements.
Included is a periodic spiral, developed from Hackh's 1914 version:
© Mark R. Leach 1999-
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counter started in 2011