Question

A, B, and C are the elements of dobereiner's triad if the atomic masses of A is 7 and that of C is 39 what should be the atomic mass of B.

Answer 1

Dobereiner stated that the arithmetic mean or average of the atomic masses of the first and third elements in a triad would be approximately equal to the atomic mass of the second element in that triad.

So the elements A, B, and C are in a triad then the atomic masses of A and B in a triad would be approximately equal to the atomic mass of the C in that triad.

The average atomic mass of B equals to $\frac{A+C}{2}$

Therefore the atomic mass of B equals to$\frac{7+39}{2}=23$.

Hence according to dobereiner's triad's B=23.