Chemistry - PERIODIC TABLE Question with Solution | TestHub

Question Explanation: Identifying sets that do not follow the law of triads.

Concept: Dobereiner's Law of Triads.

Solution: According to the law of triads, the atomic mass of the middle element should be the average of the first and third. While (Li,Na,K) and (Cl,Br,I) follow this, the sets (O, S, Se) and (N, P, As) are not considered Dobereiner's triads.

Final Answer: (c) and (d)