Question

how did dobereiner classify the elements?​

Answer 1

So, attempts were made to classify elements on the basis of their atomic masses. ... He grouped the elements with similar chemical properties into clusters of three called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element

hope it helps

Answer 2

So, attempts were made to classify elements on the basis of their atomic masses. ... He grouped the elementswith similar chemical properties into clusters of three called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element.The basis of classification of Dobereiner 's traids is atomic mass. Dobereiner arranged elements in the form of triads.In each triad the elements are arranged in increasing order of their atomic mass. The atomic mass of the middle element is equal to the average atomic mass of both the terminal elements.