Explain Dobereiner's triads giving one example.

Explanation

Dobereiner's triads:
Dobereiner suggested that properties of elements are related to their atomic masses . He classified existing elements in a tabular form by placing three elements having similar chemical properties in a group called triad.
ii. In each triad, the elements were placed according to increasing order of their atomic masses.
iii. The atomic mass of the middle element in each triad was approximately equal to the mean of the atomic masses of the other two elements.
iv. Example : In the triad of calcium, strontiu and barium, the atomic masses of calcium (40.1) and barium (137.3).