Initially Scientists had classified elements into metal and non-metals. However some elements possessed properties which could neither be metals or non-metals called metalloids. The classification was found to be insufficient for scientific study. Later on, a number of chemists attempted to male a rational and systematic classification of the physical and chemical properties of the elements and tabulate them in the form of a table.
Matter around us is present in the form of elements, compounds and mixtures.
There are total 118 elements known to us all possessing different properties.
To make the study of the elements easy they have been divided into few groups of three elements known as triads. Having similar chemical properties.
Periodic Table:- The table giving the arrangement of the known elements according to their properties so that similar elements fall within the same vertical column and the dissimilar elements are separated.