According to Dobereiner when elements of same properties are kept in the

increasing order of atomic weights, the atomic weight of middle element is

equal to the mean atomic weight of remaining two elements. Such a group of

elements is called

Dobereiner’s triad.

Dobereiner could arrange only a few elements as triads and there are some

elements present in a triad, whose atomic weights are approximately equal

Fe  Co  Ni

Ru  Rh  Pd

 

There fore, this hypothesis was not acceptable for all element

 

As in music, the eighth node is same as the first node. If the elements are

arranged in the increasing order of atomic weights, on starting with an

element, the first element will exhibit similarities with the eighth elem