History of the Periodic Table


The periodic table was proposed by Russian chemist Dimitri Mendeleev in 1869. Mendeleev arragned the elements existing at the time in order of increasing atomic weight with repetitions after definite intervals.1 Historically, it appears as if Mendeleev devised the periodic table over the course of one day. Upon waking March 1, 1869, Mendeleev noted his first ideas at breakfast on a note he had received regarding a visit to a local cheese factory he had scheduled for that day. As the day progressed, he cancelled his visit to the cheese factory in order to work on his project.

Mendeleev drew up 63 cards, representing the 63 elements known at that time. On each card he listed important chemical and physical properties of the element represent by the card. Most of his day was spent shuffling these cards, trying to devise an arrangement by which elements with similar properties would be grouped together. Finally, he came up with an arrangement quite similar to the modern periodic table. The most striking difference between Mendeleev's first table and the modern periodic table was the fact that Mendeleev's first table was arranged in horizontal rows. After awakening from a brief nap that afternoon, he transposed his table into the columns we are now familiar with.2


Probably the most impressive feature about Mendeleev's periodic table was that with it he predicted properties of elements that had not yet been discovered. Galium, scandium and germainum were three elements predicted by Mendeleev and within 20 years of his arrangement of the periodic table, all three had been discovered and found to have properties similar to those Mendeleev predicted they would have.3

Very few refinements have been made to Mendeleev's periodic table. The discovery of the noble gases in 1890 put to rest the dilemma Mendeleev had regarding just where to insert the discontinuities in his table.3 In 1913, Anton van den Broek proposed that the periodic table be based on increasing atomic number rather than atomic mass. This speculation was proved correct by Henry Moseley and cleared up some ambiguity in Mendeleev's table. Namely, the positions of cobalt and nickel, as well as argon and potassium were exchanged. This resulted in each of these atoms being grouped in a family better representing their physical and chemical properties.3,4

The periodic table was included in H.G. Deming's 1923 text book and was used as an advertising device by Merck and Co. a few years later. By the 1930s, the periodic table was a common inclusion in chemistry and physics texts.2

References

1. Scerri, E.R. American Sceintist. 1997, 85, 546-553.

2. Emsley, J. New Scientist. 7 Mar. 1985, 105, 32-36.

3. Rouvray, D. New Scientist. 12 Feb. 1997, 141, 36-39.

4. Scerri, E. Scientific American. Sep. 1998, 279, 78-83.

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