0PERIODIC TABLE- Periodic Laws- Genesis of Periodic Classification
- After the proposal of John Dalton's Atomic Theory, the scientists took Atomic Weight as the important property of element and tried to seek relationship between the properties of elements and their Atomic Weights.
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Johann Dobereiner pointed out that there were sets of three elements which showed similar chemical properties and such sets are named as Triads.
- The Atomic Weight of the middle element of a Triad was approximately the average of the Atomic Weights of the other two members.
- Examples for Triads: Li, Na and K; Ca, Sr and Ba; Cl, Br and I; etc.
