The INTERNET Database of Periodic Tables
There are hundreds 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.
One of the first attempts at a periodic table, known as "Newlands octaves", arranged the known elements by atomic weight. Newland noticed that if he broke up his list of elements into groups of seven starting a new row with the eighth element the first element in each of those groups had similar chemistry. More here.
Seeing the word octave applied to this table may lead one to think that Newlands recognised periods of eight elements with repeating properties, as we do with the modern periodic table, for example: Li Be B C N O F Ne.
However, each sequence of Newlands' octaves contain only seven elements. Count the columns! In Newlands' day the group 8 (18) rare gas elements, He, Ne, Ar, Kr & Xe, had not yet been discovered.
To Newlands, Li to Na is an octave of eight elements, the eighth element repeating the properties of the first: