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In Doberiener traid the atomic weight of middle element is 1. The Sum of the atomic weights of first and third elements 2. The product of the atomic weights of First and Third elements 3. The ratio of the atomic weights of First and Third elements 4. The mean of the atomic weights of first and third elements

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Dobereiner arranged elements as 1. groups 2. periods 3. triads 4. All the above

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Triads means 1. Small groups of Three elements 2. Small groups of Four elements 3. Small groups of Five elements 4. Small groups of Six elements

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The first classification of elements is attempted by 1. Dobereiner 2. Mendeleff 3. Mosley 4. John A.R. Newlands

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