Periodic Table |
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| What is the Periodic Table Showing? | Periodicity |
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. The database holds information on periodic tables, the discovery of the elements, the elucidation of atomic weights and the discovery of atomic structure (and much, much more).
Periodic Tables from the year 1895 :
| 1895 | Retger's Periodic Table |
| 1895 | Thomsen's Systematic Arrangement of the Chemical Elements |
| 1895 | Helium, Discovery of |
| Year: 1895 | PT id = 364, Type = formulation |
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:

| Year: 1895 | PT id = 368, Type = formulation |
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.

| Year: 1895 | PT id = 782, Type = element |
Discovery of Helium
He
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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