Question

In Dobereiner’s triad containing Li, Na, K, if atomic masses of Lithium &

Potassium are 6.9 and 39.1, then what will be the atomic mass of Sodium?

Answer 1

atomic mass of sodium = 6.9 + 39.1 / 2
= 46 / 2
= 23 g

Answer 2

The atomic mass of Sodium Na will be 23.

According to Dobereiner's law of Triads when elements are arranged in the ascending order of their atomic masses, groups of 3 elements or triads are formed, where the atomic mass of the middle one will be an apporximate average of the other elements.

So it 6.9 + 39.1 / 2 = 23