Question

Dobereiner's law of triads states that, the atomic mass of the middle element of a triad is the arithmetic mean of the atomic masses of the other two elements

Answer 1

Yes it's true.

Ex: Li. Na. K

At.wt of :

Li-7; K - 39. Finding the arithmetic mean 39+7/2=23 ,the at.wt of Na.

Other ex: Ca,Sr,Ba & Cl,Br,I.