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.
Use the buttons below to select from the 1000+ Periodic Tables in the database:
Discovery of Neptunium
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.
© Mark R. Leach 1999-
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