Question

9) Which one of the following is the example of triad

a) Li, Na, Rb b) Ca, Mg, K c) Fe,Mn,S d) Cl,Br,I ​

Answer 1

Answer:

Option A is your answer.

Dobereiner stated in his law of triads that the arithmetic mean of the atomic masses of the first and third element in a triad would be approximately equal to the atomic mass of the second element in that triad. He also suggested that this law could be extended for other quantifiable properties of elements, such as density.

This triad was made up of the alkali metals lithium, sodium, Rubidium.

Atomic mass of lithium is 6.94

Atomic mass of Sodium is 22.99

Atomic mass of rubidium is 85.46

The arithmetic mean of the masses of Rubidium and lithium , which is almost equal to the atomic mass of sodium.

Therefore it is a triad.