Question

The three elements A,B and C with simlar
properties have atomic masses X,Y and
Z. respectively. The
mass of Y is approximatelty equal to
the average mass of x and z. what is
such an arrangement of elements called
as? Give one
example of such a set of
elements.​

Answer 1

Answer:

Such arrangements of elements are given by DOBERINER (1817)... He gave a rule known as Triad rule...

Explanation:

Example: ➡ Li, Na and K...

Mass of Lithium- 7 (X)

Mass of Sodium- 23 (Y)

Mass of Potassium- 39 (Z)

➡Y = (X + Z)/2

➡ Y = (7 + 39) /2

➡ Y = 46/2

➡ Y = 23

Hence, rule satified here... But not applicable to every element of a group....