The Periodic System
A Bit of History...
Classification not only makes possible the systematic description of objects and phenomena but also points out the directions in which investigation may lead to new facts of moment. Hence classification is a necessary and very important factor in the development of a science.
Soon after the advancement of the atomic theory by Dalton, began to develop the idea that not all atoms could be entirely unlike but that atoms of one element might have properties somewhat similar to those of some other element. With the increase in number of the known elements through new discoveries, more interest in the problem of their classification developed.
As a result many arrangements were proposed.