Historically, there have been a number of attempts to organize our knowledge of the chemical elements into useful formats:
- Late 18th century: Lavoisier's list of 28 elements
- Early 19th century: John Dalton's list of approximately 60 elements
- Döbereiner's "triads" of elements with related or similar properties; e.g., Ca, Sr and Ba
- John Newlands "octaves" or groups of eight elements after which properties seemed to repeat
Both Döbereiner and Newlands were on the right track but they were hampered by missing information. In 1870 there were only 65 elements known. Elements missing in critical positions in the early classification schemes caused problems. Two scientists eventually came up with a successful arrangement of the known elements independently of one another.