The periodic table merges scientific inquiry, international politics, hero worship, desires for structure and desires for credit.
Formally, the modern periodic table is a systematic arrangement of the known chemical elements. The table is organized in an orderly way that shows the periodic occurrence of elements with similar chemical properties. Elements with similar chemical properties are stacked one on top of another in columns; going down each column from one row to the next the atoms of the elements get larger and heavier. Such periodic variations in the properties of elements are what Dmitri Mendeleev (1834-1907) and other scientists observed and sought to summarize in tabular and other forms.
Yet, the periodic table is not as objective as that basic description may sound. And who deserves credit for its creation is also not straightforward. I am a theoretical chemist; I apply chemical principles and mathematics to answer questions and solve problems in various areas of chemistry. I’m also fascinated by the history of science and how we assign credit and name things in science. Those interests coupled with my chemistry background have led me over the years to intersections of the political and the scientific in the emergence of the modern periodic table.
There are, for instance, nationalistic tilts to the periodic table. Two elements (francium and gallium) are named for France and one each for Japan (nihonium), Germany (germanium) and Poland (polonium). Scandinavia got scandium; the elements berkelium, darmstadtium and moscovium give three cities each a spot on the table. One Swedish village – Ytterby – has claimed four elements: erbium, terbium, ytterbium and yttrium. A number of other places and people have also snagged their little rectangles on the table too, and that, in some cases, only after serious disputes.
Among the elements named after people is element number 101, mendelevium (Md), which honors Mendeleev. Resisting other self-serving instincts, a group of Berkeley scientists who discovered the radioactive Md in 1955 decided to honor the Russian scientist Mendeleev for his contributions to formulating the periodic table. With the Cold War underway, however, they had to convince the Eisenhower administration to allow them to give up a spot on the table to a deceased Russian.
Why Mendeleev, though? Did he discover the periodic table? Hardly.
Mendeleev published in 1869 a paper that organized then-known elements in an authoritative, logical and systematic way, and he boldly predicted new ones. That paper was followed by others in the early 1870s that improved on the first and demonstrated the value of a deep appreciation for the periodicity in chemistry.
He, his papers and his table garnered a lot of attention and accelerated progress in our collective understanding of the elements and their relationships to each other. But the inspiration and the data that spurred Mendeleev’s achievements were owed in huge ways to predecessors and contemporaries such as Amedeo Avogadro (1776-1856), Johann Wolfgang Döbereiner (1780-1849) and Stanislao Cannizzaro (1826-1910).
At the end of a chemical congress in Karlsruhe, Germany, in September 1860, for instance, a decisive paper by Cannizzaro on the weights of the atoms of the elements was distributed to the attendees. Mendeleev was at that meeting, and Cannizzaro’s work helped him to organize his 1869 table of 63 known elements, which he arranged according to observed chemical properties and assigned atomic weights.
Cannizzaro’s work was so convincing that another attendee of the Karlsruhe meeting, J. Lothar Meyer, reported that it felt to him as if the scales fell from his eyes as he gained a new understanding of the elements.
Mendeleev’s periodic chart appeared some nine years after the Karlsruhe meeting (1869), but by 1868 Alexandre-Émile de Chancourtois (1820-1886), William Odling (1829-1921), John Newlands (1837-1898) and Gustavus Hinrichs (1836-1923), for example, had already served up, however technically inferior, credible attempts at periodic assemblies of the elements. Newlands had also predicted the existence of other elements.
Meyer, enlightened as he was by Cannizzaro, devised tables in the 1860s before Mendeleev’s appeared. But his grand paper describing his table, which was similar to Mendeleev’s in many respects, was published in 1870, some months after Mendeleev’s 1869 paper. Predictably, a slowly festering dispute over priority eventually erupted between them.