Three elements A, B and C with similar properties have atomic masses X,Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called? Give one example of such a set of elements.

Three elements A, B and C with similar properties have atomic masses X

1.	Three elements A, B and C with similar properties have atomic masses X,Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called? Give one example of such a set of elements.
Answer» Solution :The arrangement of these elements is known as Dobereiner.s triad. E.g ONE set of triad is LITHIUM, SODIUM and POTASSIUM