Wall chart with the periodic table of the elements, maker: Ernst Klett Verlag/Stuttgart, 1962, 194.7 × 133.3 cm (without rods). Bismarck-Gymnasium Karlsruhe.
The arrangement of the chemical elements in the periodic table is familiar to most people from school, often depicted on a wall chart or scrollable screen. Illustrations of the periodic table are widespread, even appearing as household decor on items like shower curtains. The knowledge systematically presenting the constituents of matter as atoms and their various properties, has a long history. The first International Congress of Chemists, held in Karlsruhe in 1860, aimed to establish a common definition of the atom. Although this meeting did not immediately reach the desired consensus, the findings shared there laid the groundwork for a systematic ordering of the chemical elements. Two participants at the Karlsruhe Congress, Dmitry Mendeleyev (1834–1907) and Lothar Meyer (1830–1895), almost concurrently drafted the periodic table entirely independently of each other in 1869. At that time, Meyer was a chemistry professor at Karlsruhe Polytechnical College. The Chemical Institute, established by his predecessor Karl Weltzien (1813–1870), conducted both research and teaching. This integration of the two tasks was not yet commonplace at Karlsruhe Polytechnical College. The discipline of chemistry thus provided crucial impetus for the further development of the institution as a whole. kn
The periodic system of the elements (PSE) is a tabular listing of all chemical elements, arranged by increasing atomic number. Elements with the same number of electron shells are placed next to each other in periods. Elements with similar chemical properties are grouped vertically into columns. Historically, the PSE was crucial for the prediction and discovery of new elements and their properties. In December 1869, Lothar Meyer, a professor of chemistry in Karlsruhe, described the PSE in an article in Annalen der Chemie und Pharmacie. Meyer had previously outlined a similar table in his textbook from 1864, Die modernen Theorien der Chemie. However, when UNESCO declared 2019 as the International Year of the PSE, it referred not to Lothar Meyer, but to the publication of a periodic table by the Russian chemist Dmitry Mendeleyev in July 1869. In recognition of both their contributions, Mendeleev and Meyer were jointly awarded the Davy Medal of the Royal Society in 1882 for their researches into the classification of the elements. Of decisive influence on Mendeleyev and Meyer’s work on the periodic table was their participation in the Karlsruhe Congress of Chemists in September 1860. This first international conference of the emerging science of chemistry, attended by 127 chemists, was organized by Karlsruhe chemistry professor Karl Weltzien along with two colleagues from France and Belgium. The goal was to clarify fundamental questions of chemical structure theory through discourse with fellow specialists. The contribution by the Italian chemist Stanislao Cannizzaro (1826–1910) provided significant impetus for Mendeleyev’s and Meyer’s conception of the PSE. Building on the ideas of his compatriot Amedeo Avogadro (1776–1856), Cannizzaro clarified the then highly controversial issue of calculating atomic weights. Lothar Meyer later reflected on this breakthrough: “The scales fell from my eyes, the doubts vanished, and a feeling of calmest certainty took their place. […] Many other participants at the meeting must have felt the same way as I did.” Michael Mönnich