would rationalize known chemical facts about elements, but even predict new ones for undertaking further study. . GENESIS OF PERIODIC CLASSIFICATION Classification of elements into groups and development of Periodic Law and Periodic Table are the consequences of systematising the knowledge gained by a number of scientists through their observations and experiments. The German chemist, Johann Dobereiner in early ’s was the first to consider the idea of trends among properties of elements.
By he noted a similarity among the physical and chemical properties of several groups of three elements ( Triads ). In each case, he noticed that the middle element of each of the Triads had an atomic weight about half way between the atomic weights of the other two (Table . ). Also the properties of the middle element were in between those of the other two members.
Since Dobereiner’s the periodic recurrence of properties. This also did not attract much attention. The English chemist, John Alexander Newlands in profounded the Law of Octaves . He arranged the elements in increasing order of their atomic weights and noted that every eighth element had properties similar to the first element (Table .
). The relationship was just like every eighth note that resembles the first in octaves of music. Newlands’s Law of Octaves seemed to be true only for elements up to calcium. Although his idea was not widely accepted at that time, he, for his work, was later awarded Davy Medal in by the Royal Society, London.
The Periodic Law, as we know it today owes its development to the Russian chemist, Dmitri Mendeleev ( - ) and the German chemist, Lothar Meyer ( - ). Table . Dobereiner’s Triads Element Atomic weight Element Atomic weight Element Atomic weight K Ca Sr Ba Cl Br I . Table .
Newlands’ Octaves Element Be B C N O F At. wt. Element Mg Al Si P S Cl At. wt.
. Element K Ca At. wt. relationship,