German chemist who developed the Law of Triads in 1829 in an early attempt to classify the chemical elements. This law organized elements in groups of three having similar properties (such as chlorine, bromine, and iodine) and stated that the average mass of the first and third equaled the mass of the second. This law is approximately true for several groups of elements. Döbereiner's classification scheme was improved and perfected by Mendeléev.

Beguyer de Chancourtois, Dumas, Mendeléev, Meyer, Newlands