The periodic system arose from patterns in physical and chemical behaviours of the known substances by mid 19 th century. It was through substances -constituting the chemical space-, that regularities in the similarities among chemical elements were detected and that elements could be ordered . With the passage of time, the system has been adjusted to accommodate new elements but the original connection between the system and its supporting chemical space has been largely forgotten . In the current paper we analysed how the unfolding of the chemical space between 1800 and 2021 has affected the periodic system, that is the structure of order and similarity among chemical elements . As order is ruled by atomic number, which is invariant to changes in the chemical space; whereas similarity is determined by the kind and diversity of compounds housed by the chemical space at a given time, studying the evolution of the periodic system entails analysing the effect of the chemical space upon similarities among chemical elements. By studying these similarities over time, we found that despite the exponential discovery of new chemical substances , the periodic system has historically converged to an arrangement of families of similar elements. Evidences of such a convergence are found as early as the first quarter of the 19 th century, where the corner stone of the periodic system arose by the appearance of alkali metals, some transition metal groupings, pnictogens, chalcogens and halogens.