Question

Three elements X, Y and Z formed a dobereiner's triad. The ratio of the atomic weight of X to that of Z is 7:25, if the sum of atomic weight of X and Z is 160, find the atomic weight of X, Y and Z.

Answer 1

• According to Dobereiner's triad, certain elements with comparable chemical properties can be grouped together. When these comparable elements are placed in ascending order of their atomic masses, they usually form a group of three, with the center element's atomic mass equal to the arithmetic mean of the other two elements. Triads were the name for a group of three elements.
  As a result of this law, when the elements are ordered by increasing atomic mass, a group of three elements with similar qualities known as triads is formed, with the atomic mass of the middle element equal to the arithmetic mean of the other two elements.
• The atomic weight ratio of X and Z is $7:25$, and their total weight is$160.$
• So,$7x+25x=160$
• $$\begin{gathered} \Rightarrow 32x=160 \\ \Rightarrow x=5 \end{gathered}$$
• As an outcome of the atomic weights of $X=35$ and $Z=125$, Dobereiner's triad was established. Since the weight of Y is composed of the weights of X and Z according to Dobereiner's triad.
• Hence, Y's atomic weight:
• $=\frac{35+125}{2}=80$