Question

A, B and C are the elements of a Dobereiner’s triad. If the atomic mass of A is 7 and that of C is 39, what should be the atomic mass of B ?

Answer 1

A, B and C are the elements of a Dobereiner's triad. If the atomic masses of A and C are 7 and 39 respectively, then according to Dobereiner's triad law, the atomic mass of B is the average of the atomic masses of A and C.

So, the average of the atomic masses of A and C = $\frac{(7+39)}{2}=\frac{46}{2}=23$
Therefore, the atomic mass of B is 23.