Internet Database of Periodic Tables
There are thousands 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.
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The Karlsruhe Congress of 1860 was called so that European chemists could discuss a number of issues, including atomic weights.
From Wikipedia (lightly edited):
"The Karlsruhe meeting ended with no firm agreement on the vexing problem of atomic and molecular weights. However, on the meeting's last day reprints of Stanislao Cannizzaro's 1858 paper on atomic weights were distributed. Cannizzaro's efforts exerted an almost immediate influence on the delegates.
"Lothar Meyer later wrote that on reading Cannizzaro's paper: 'The scales seemed to fall from my eyes.'
"An important long-term result of the Karlsruhe Congress was the adoption of the now-familiar atomic weights. Prior to the Karlsruhe meeting, and going back to Dalton's work in 1803, several systems of atomic weights were in use.
"Following the Karlsruhe meeting, values of about 1 for hydrogen, 12 for carbon, 16 for oxygen, and so forth were adopted. This was based on a recognition that certain common gaseous elements, such as hydrogen, nitrogen, oxygen and chlorine were composed of diatomic molecules and not individual atoms: H2, N2, O2, Cl2, etc."
Once enough elements had been discovered, and their atomic weights correctly deduced, the time was ripe to develop versions of the periodic table systems. These came 'thick & fast' after the Karlsruhe Congress.
Many thanks to Carmen Giunta, Professor of Chemistry Emeritus, Le Moyne College who provided the information about the important Karlsruhe Congress.
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