chapter -5 Periodic Classification of Elements
Periodic Classification of Elements Chapter -5 Introduction to Periodic Classification of Elements Why Classification? Without the classification of elements, it would be extremely difficult and time-consuming to individually study the chemistry of all the elements. Hence, to simplify and systematize the study of elements and their compounds, they are classified into groups and periods. Early Models of Periodic Table Dobereiner’s Triads Dobereiner arranged a group of three elements with similar properties in the order of increasing atomic masses and called it a triad. He showed that the atomic mass of the middle element is approximately the arithmetic mean of the other two. But, Dobereiner could identify only the following three triads from the elements known at that time. Newlands’ Law of Octaves sa (do) re (re) ga (mi) ma (fa) pa (so) da (la) ni (ti) H Li Be B C N O F Na Mg Al Si P F Cl K Ca Cr Ti Mn Fe Co and ...