Johann Dobereiner



Johann Wolfgang Döbereiner (1780–1849), simply as Johann Dobereiner, was a German chemist whose observation of similarities among certain elements anticipated the development of the periodic system of elements. He observed that groups of three elements (triads) could be formed in which all the elements shared similar physical and chemical properties. Döbereiner stated in his law of triads that the arithmetic mean of the atomic masses of the first and third element in a triad would be approximately equal to the atomic mass of the second element in that triad. He also suggested that this law could be extended for other quantifiable properties of elements, such as density.

The first of Dobereiner’s triads was identified in the year 1817 and was constituted by the alkaline earth metals calcium, strontium and barium. Three more triads were identified by the year 1829.