Question

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Answer 1

dobereiner was a great scientist. who put forth his traid.doberiener make group or cluster of three elements and called them traid.According to him the atomic mass of middle element was exact mean of other elements. for eg if we consider elements mg,ca,sr then the atomic mass of calcium was equal to mean of atomic mass of magnesium and strontium. doberiener arranged this elements according to rise in atomic mass of elements and he put forth this classification in 1817