Question

How did dobereiner classify the elements? Give one example. What were the limitations of his classificationa'

Answer 1

He showed that when three elements in triad were written in order of their increasing atomic masses,the atomic mass of the middle element was roughly the average of the atomic masses of the other two.

Example: in the triad Li,Na andK, the atomic mass of Na(23) is the average of atomic masses of Li and K {(6.9+39)/2=23}.

Limitation: 1. Dobereiner could identify only those three triad from the elements known at that time.

2. He was not confirmed for future predicted element.

Answer 2

According to Dobernier traid if the elements are arranged according to their increasing atomic masses and forms a traid then atomic mass of the middle element will be equal to the average atomic mass of other two elements.

Example -

Element Li Na K

At. mass 6.9 23 39

Limitations :-

1. Dobernier could identify only three traids from the elements known at that time

2. Dobernier assumed that no more elements would be discovered in the future.

Hope it helps.......