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 hold information on periodic tables, the discovery of the elements and elucidation of atomic weights (and more).
| Year: 1979 | PT id = 994, Type = formulation review |
Seaborg's "How the Periodic Table Evolved Over 40 Years" (1939 – 1979)
From the C&EN paper THE PERIODIC TABLE: Tortuous path to man-made elements 57, 1979, pp 46-52.
Until World War II, the three heaviest known elements – thorium, protactinium & uranium – were believed to be related to hafnium, tantalum & tungsten respectively. Similarly, elements 93 to 100 were expected to fit neatly into the periodic table:
Synthesis and study of the transuranic elements – neptunium & plutonium – indicated that these new elements were "cousins" of uranium and in 1944 should be placed into a new "uranide" group.
Subsequently (1944/45), Seaborg advanced the theory that elements heavier than actinium actually constitute a distinct "actinide" group that mirrors the lanthanide rare-earth group:
Finally, Seaborg postulated what a future periodic table, up to Z = 168, may look like:
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| What is the Periodic Table Showing? | Periodicity |
© Mark R. Leach Ph.D. 1999 –
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