UPSEE Solved Model Paper 4

Döbereiner's triads were an early attempt to sort the elements into some logical order by their physical properties. It was discovered by reported Johann Wolfgang Döbereiner's in 1817.He also noted that quantifiable properties of elements (e.g. atomic weight and density) in a triad followed a trend whereby the value of the middle element in the triad would be exactly or nearly predicted by taking the arithmetic mean of values for that property of the other two elements.