Try to think about Dobrainer's triads and work out the base of classification

It is one of the multiples as it refers to Octaves

Think about the Newlands classification structure.

Try to memorize the total number of elements discovered

Think about the last element in the Octaves

Think about the basis of classification of the triads given by Dobrainer

Try to think about the most important aspect of classification of elements

Work out the average of the atomic masses two extreme elemnts and compare it to that of the middle element

Think about Dobrainer's triads and work out the base of classification

Try to think the classification by Newlands and then think about the order of elements according to the increasing atomic masses.