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: Dr Mark R Leach.
Use the buttons below to select from the 1000+ Periodic Tables in the database:
Discovery of Thorium
Thorium, atomic number 90, has a mass of 232.038 au.
Radioactive element with a very long half-life.
Thorium was first observed or predicted in 1829 by J. Berzelius and first isolated in 1914 by D. Lely, Jr. and L. Hamburger.
© Mark R. Leach 1999-
Queries, Suggestions, Bugs, Errors, Typos...
If you have any:
This free, open access web book is an ongoing project and your input is appreciated.