Question

why was the law of triads rejected for classifying elements

Answer 1

Hey there! here is ur answer-

Only three triads could be formed.

Li, Na, K

Ca, Sr, Ba

Cl, Br, I

So for the rest of the elements it proved to be useless. The property was that the average atomic mass of the element in the middle was equal to the average of the atomic masses of the other two elements. It was useless because not all elements could fit into this property.

*Hope* it helps u :-)

Answer 2

The law of triads was rejected because Doberiener failed to arrange all the known elements in form of triads.Besides,The law did not fully apply within the same family.  Note_The atomic mass of the middle element of a triad was approximately equal to arithmetic mean (average)of the atomic masses of the other two elements of that triad.But,taking halogens,viz. the first three members ,Flourine (19),chlorine(35.5)and bromine(80),it is observed that the mean of the atomic masses of Flourine and bromine is 1/2(19+80)=49.5,not 35.5.  So,Dobereiner's scheme of classification of elements was not very successful,though it did contain important insights and principles.   ....By Alison Stephanie.