Question

Three elements calcium, strontium, and barium from a Döbereiner's triad. What is the basis on which these elements are arranged in a triad?
i. Elements are in the increasing order of their atomic weights.
ii. The atomic mass of the middle element is equal to the average of the atomic mass of other two elements.
iii. Elements in a triad have similar physical and chemical properties.

• A. (i) and (iii)
• B. (ii) and (iii)
• C. (i) and (ii)
• D. (i), (ii), and (iii)

Answer 1

The correct option is D (i), (ii), and (iii)

The atomic mass of calcium, strontium, and barium are 40 u, 87.6 u, and 137.3 u respectively.

Döbereiner's Triads:

• Elements are arranged in groups of three in the increasing order of atomic mass. The element with the lowest atomic mass is written first and the element with highest mass is written as the third element.
• Atomic mass of the middle element is approximately the average of mass of the other two elements.
• Elements in a triad have similar physical and chemical properties.

Hence of the given statements are true.
Correct option: (d)