Which of the following is NOT a Döbereiner’s triad?

Correct option is B

Correct Answer: (b) Ca, Br and I
Explanation:
· A Döbereiner’s triad consists of three elements with similar chemical properties where the atomic mass of the middle element is the average of the other two.
· In option (b), Ca (Calcium), Br (Bromine), and I (Iodine) do NOT belong to the same group and cannot form a triad.
· Thus, (b) is NOT a Döbereiner’s triad.
Information Booster:
· Johann Döbereiner identified the following valid triads:
· Li, Na, K (alkali metals)
· Ca, Sr, Ba (alkaline earth metals)
· Cl, Br, I (halogens)
· S, Se, Te
· In these, the atomic mass of the middle element ≈ average of the other two.