Question

what was the earliest classification of element

Answer 1

Earlier attempts of classification of Elements

Johann Dobereiner Triad model

The first attempt on classification of elements have no definite proof as early man started to classify elements based on his needs. But a scientific method of classification was first introduced by the German chemist Johann Dobereiner in 1829. He classified the elements to groups of three. It should be noticed that there was only less number of elements at that time and many were not discovered. A classification method at that time therefore really deserve appreciation. Dobereiner thus created a law based on his classification and was called Law of Triads.
The name triads came as his classification included elements in a group of three. He also noticed that there was relation in the classified group. The middle element, ie, the second element was having somewhat an atomic mass which was equal to the average mass of other two elements in the group. This was the basis of Law of Triads.