Question

With an example, explain Dobereiner's Triads.

State Dobereiner’s Triads giving one example.

Answer 1

Dobereiner arranged chemically similar elements in the increasing order of their atomic weights in a group of three which is known as “Dobereiner’s triads”. In a Triad, the atomic mass of the middle element is approximately equal to the mean of atomic masses of the other two elements in that triad.

Examples:

1. Lithium, Sodium, Potassium.
2. Calcium, Strontium, Barium.
3. Chlorine, Bromine, Iodine.

Answer 2

According to Dobereiner's Triads, when three elements in a triad are listed in the increasing order of their atomic masses, the atomic mass of the middle element will roughly be the average of the atomic masses of the other two elements.

For e.g.:

Element	Atomic mass
Calcium	40
Strontium	88
Barium	137

Average mass of calcium and barium = `(40+137)/2 = 88.5`