Question

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

Answer 1

Mass of B is 23.  

Explanation:

According to Dobereiner the atomic weight of middle element is nearly the same as average of the atomic weight of other two elements.

Here, Atomic Mass of A = 7

Atomic Mass of C = 39

So, Atomic Mass of B = $\frac {A+C}{2}$

= $\frac {7+39}{2}$

= $\frac {46}{2}$

= 23

Atomic Mass of B - 23