Previous methods for quantifying similarity among elements, consider the complete replacement of one element for another in chemical formulas . Thus, given the formula C 6 H 6 , to capture some similarity between H and Br, the existence of C 6 Br 6 would be required in the chemical space . Although valid, the complete replacement of one element for another represents only a small sample of the possible replaceabilities actually observed in substances, consequently missing important patterns leading to similarities. Our approach to similarity considers the fact that single atoms can also be independently replaced within molecular formulas, as is the case of the compounds C 6 H 6 and C 6 H 5 Br, which differ only by substitution of one H for one Br. These are similarity patterns more common to chemist's experience. Their computation brings the additional advantage of increasing the dataset size -by leveraging each element's subindex within a compound-, allowing for the extraction of richer patterns, which is specially important in low-data regimes such as the early 19 th century .