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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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Periodic Tables from the year 1895:

1895   Retger's Periodic Table
1895   Thomsen's Systematic Arrangement of the Chemical Elements
1895   Discovery of Helium


Retger's Periodic Table

Periodic Table of Retgers with an intraperiodic accommodation of the rare earths. Retgers, J.W., 1895. Z. Phys. Chem. 16, 644:

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Thomsen's Systematic Arrangement of the Chemical Elements

In 1895 the Danish thermochemist Hans Peter Jørgen Julius Thomsen proposed (Thomsen, J., 1895. Z. Anorg. Chem. 9, 190 & Chemical News, 72, 89–91, p. 90) a pyramidal/ladder representation.

Notice how this formulation identifies the electropositive & electronegative elements with respect to the periodic table, thirty years before Linus Pauling.

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Discovery of Helium


Helium, atomic number 2, has a mass of 4.003 au.

Helium is a noble gas, and is the second most abundant element in the universe after hydrogen.

Helium was first observed or predicted in 1868 by P. Janssen and N. Lockyer from solar spectra, and first isolated in 1895 by W. Ramsay, T. Cleve, and N. Langlet.

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What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –

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