Periodic Table
T-Shirts & more
from the

Merch Store

previous home next

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 1300 Period Tables in the database: 

  Text Search:       

Year:  1949 PT id = 1052

Catalán's Periodic System/Sistema Periodico Ampliado

Two versions of Catalán's Periodic System/Sistema Periodico Ampliado. The first from C.E. Moore 1949, Atomic Energy Levels, National Bureau of Standards, Circular no. 467, Washington DC, vol. 1, table 25 (1949) and the second as referenced here:

René Vernon, who provided the graphics, writes:

"I feel the footnote along the base of the first table could merit better attention being drawn to it. It says:

This arrangement is by Catalán. The electrons indicated in column two that are connected by braces have approximately the same binding energy. Consequently, for some elements one type of electron is preferred over another in the normal configuration, as for example, Cr, Cb, Pd, La, Ac, Th.

"The connecting braces hone in on the source of much of the controversy concerning notions of an ideal, optimal, better, this or that, or fundamental periodic table. I can't recall seeing a table with such a feature. For the second table, turning it on its side (attached) reminds of the ADOMAH [formulation].

Click on the images to enlarge:

Thanks to René for the tip!

Top of Page

previous home next
What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –

Queries, Suggestions, Bugs, Errors, Typos...

If you have any:

Suggestions for links
Bug, typo or grammatical error reports about this page,

please contact Mark R. Leach, the author, using

This free, open access web book is an ongoing project and your input is appreciated.