The Periodic Table is the most important concept in chemistry, both in principle and in practice. It is the everyday support for the students, it suggests new avenues of research to professionals, and it provides a succinct organization of the whole of chemistry. It is a remarkable demonstration of the fact that the chemical elements are not a random cluster of entities but instead display trends and lie together in families. An awareness of the Periodic Table is essential to anyone who wishes to disentangle the world and see how it is built up from the fundamental building blocks of the chemistry, the chemical elements. - Glenn T. Seaborg
In this unit we will study the historical development of the Periodic Table as it stands today and the Modern Periodic Law. We will also learn how the Periodic classification follows as a logical consequence of the electronic configuration of atoms. Finally, we shall examine the Periodic trends in the physical and chemical properties of elements.
At present, one hundred eighteen elements are known. These elements form a large number of compounds. A systematic study of these elements as; their compounds is possible only when these element; are arranged in such a manner that the arrangements closely related to their properties and makes the study simpler.
Significance of classification of elements
Inorganic chemistry deals with elements and their compounds. Elements are the basic units of all types of matter. In year 1800 only 31 elements were known. While in year 1885, the number of identified elements were 63. The discovery of elements gained big momentum in eighteenth and nineteenth centuries and several new elements were discovered. With the discovery of more and more elements, the chemists began to realize that these elements should be arranged in a proper way to facilitate their systematic study. The elements and their compounds (quite large in number) showed a great variation in their chemical behaviour and it was not possible to study them in a haphazard manner. To ease out this problem, scientists searched for systematic way to organize their knowledge by classifying the elements. Several efforts were made to classify the known elements in a systematic way. Not only that, it would rationalize known chemical facts about elements, butt even predict new ones for undertaking further study.