Scientists tried to classify the elements multiple times, earliest attempt to classify the elements resulted in grouping the then known elements as metals and non-metals. Döbereiner’s Triads Johann Wolfgang Döbereiner, a German chemist, tried to arrange the elements with similar properties into groups. He showed that when the three elements in a triad were written in the order of increasing atomic masses; the atomic mass of the middle element was roughly the average of the atomic masses of the other two elements. triad consisting of lithium (Li), sodium (Na) and potassium (K) with the respective atomic masses 6.9, 23.0 and 39.0 Li Ca Cl Na Sr Br K Ba I triads of elements which led to the development of the Periodic Table of elements Newlands’ Law of Octaves John Newlands, an English scientist, arranged the then known elements in the order of increasing atomic masse...