_______ scientist noticed that atomic weights of many pairs of elements which differed by eight or a multiple of eight exhibited similarities in their chemical properties. 

In 1864, the English Chemist, John Newland arranged the then known 56 elements in an increasing order of their atomic weights. He noticed that atomic weights of many pairs of elements which differed by eight or a multiple of eight exhibited similarities in their chemical properties. Based on this observation, he proposed the law of octaves.