Question

Atomic mass of X and Z is 20 and 40 respectively. If X, Y and Z is Dobereiner's Triad. What can be the atomic number of Y?

• A. 20
• B. 40
• C. 30
• D. All of these

Answer 1

The correct option is C

30

The mass of middle element was roughly the average of atomic masses of other two elements in Doberner's triad. Since Y is the middle element of the triad, its mass should be the average of 20 and 40, i.e. 30.