Question

Can the following groups of elements be classified as Dobereiner's triad:
Be, Mg, Ca
Atomic mass of Be - 9, Mg - 24, Ca - 40.
Justify your answer.

Answer 1

According to Dobereiner's triad, the atomic mass of the second element is nearly equal to the average of the atomic masses of the first and the third elements provided the three elements are arranged in the increasing order of their atomic masses.

Be, Mg, Ca:
Atomic mass of Be - 9, Mg - 24, Ca - 40
Average of atomic masses of Be and Ca = `(9 + 40)/(2) = 24.5` which is nearly equal to the atomic mass of Mg i.e. 24.
Thus, it can be considered as Dobereiner's triad.