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The INTERNET Database of Periodic Tables

There are thousands of periodic tables in web space, but this is the only comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Mark R. Leach Ph.D.

Use the drop menus below to search & select from the more than 1100 Period Tables in the database:

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Sommerfield's Electon Filling Diagram

Arnold Sommerfeld diagram appears in an issue of Memoirs and Proceedings of the manchester Literary and Philosophical Society for 1925-26. volume 70, p. 141-151.

Eric Scerri writes:

"The electron groupings are not exactly the same as what is believed to exist today but it amounts to the same order of filling. For example p orbitals were thought to consist of two groups of 2 and 4 electrons, rather than 2, 2, 2 as believed today. Similarly d orbitals were thought to be formed of two groups of 4 and 6 electrons. With that in mind you will see that Sommerfeld was the first to propose an aufbau filling system: The occupation of 4s before 3d or as represented here the 2 electrons in orbit 11 followed by the 4 and 6 from orbits 3,s and 3,3.

"Sommerfeld does indicate sub-shells. They are just not the same groupings as the current ones. For example 2,1 and 2,2 indicates subshells within the 2nd main shell. Similarly the 3rd shell is presented as 3,2 and 3,3. The totals are of course the same, namely 6 for what we now call p orbitals and 10 for what we call d orbitals. All this came before the discovery of the 4th or spin quantum number. This is in keeping with Bohr's original assignment of shells and sub-shells.

"The discovery of sub-structure to electron shells was not an 'all or nothing' development, but a gradual and almost organic evolution."

Eric has a new book out – A Tale of Seven Scientists and a New Philosophy of Science – in which the gradual evolution of electronic structure involving Bohr, Sommerfeld, Bury, Main Smith, Pauli and others is traced out.

Thanks to Eric Scerri for the tip! 
See the website and Eric's Twitter Feed

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What is the Periodic Table Showing? Periodicity

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