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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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1940

Discovery of Neptunium

Np

Neptunium, atomic number 93, has a mass of 237 au.

Radioactive element: Np is only found in tiny amounts in nature. Most samples are synthetic.

Neptunium was first observed in 1940 by E.M. McMillan and H. Abelson.

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What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –


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