Introduction to Periodic Classification of Elements

In this article we are about to learn how the elements were discovered and how they adjusted in today Periodic Tables with exact values. I'm going to show you guys, simple introduction to Periodic Classification of Elements.

Introduction to Periodic Classification of Elements

Introduction

The aim of the classification of the elements is to group together those elements which resemble each other in some respect and to separate those elements which are differ significantly. The best classification will clearly be that which brings together elements which resemble one another in the greatest number of ways.

In this way, there were some of best scientist of that time discovered 3 laws for separating the elements which are significantly similar in their properties.

1. Dobereiner's Triads

After the acceptance of atomic mass values universally, attempts were made to find out relations between properties of the various elements and their atomic masses. In 1829, J.W Dobereiner discovered that within a group of elements of three closely related in chemical properties, the atomic masses are either nearly the same (e.g. Iron, cobalt and nickel) or the atomic mass of the middle one element is the approximately the arithmetic mean of the other two elements. These are called Dobereiner's Triads.

The Graph of Dobereiner's Triads of Elements Classifications

2. Newland's Law of Octaves

The next attempt was made by an English chemist Newland between 1864-1869. He arranged the elements in the ascending order of their atomic weights (masses). He observed that the properties of every eighth element were similar to those of the first. he called this regularity of elements as the "Law of Octaves" and arranged most of the elements then known accordingly.

Newland's arrangement of element

Li= 7      Be=9.4    B=11    C=12    N=14    O=16    F=19

Na=23   Mg=24    Al=27.3    Si=28    P=31    S=32    Cl=35.5

In this classification, Li and Na and Mg; B and Al; C and Si; N and P, O and S; and F and Cl resemble in chemical properties.

Advantages and disadvantages of law of Octaves

i) This law provided a basis for the classification of elements into groups of elements having similar properties.

ii) This law provided a wider scope to arrange all known elements into a tabular form.

iii) The periodic arrangement of elements did not include noble gases because they were not discovered then, and the heavier elements could also not be accommodated.