By Ron B. Davis Jr., Georgetown University
In September 1860, the first great international gathering of chemists was held in Karlsruhe, Germany. The conference was organized in an attempt to get everyone to agree on a uniform system of measuring and reporting experimental results. The hope was that this would make scientific discourse more productive. In addition to notation and nomenclature, a major issue that was discussed was how best to measure and report on atomic weights.
Alexandre-Émile Béguyer de Chancourtois
Surprisingly, the first periodic arrangement of the elements to appear after Karlsruhe, was created not by a chemist, but by a French geologist. Perhaps even more surprising is that his system wasn’t a table at all, but rather a three-dimensional spiral.
Alexandre-Émile Béguyer de Chancourtois had decided to explore any relationships he could find between atomic weights and their other properties. To go about this, in 1862, he arranged all the known elements on a diagonal, with their position on that diagonal proportional to the atomic weight of each element.
For example, hydrogen is plotted at the coordinate 1,1; lithium appears at 7,7 and so on. He noticed that if this diagonal is not drawn as a continuous straight line, but rather is looped every 16 units of atomic mass, periodic trends in properties begin to emerge.
In this arrangement, elements with similar properties appeared in successive vertical slices of the resulting helix. For example, fluorine, chlorine, bromine, and iodine all appear together in the same vertical slice.
This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.
The Telluric Helix
De Chancourtois’ creation was a three-dimensional helix that could be turned to view the relationships among the elements. Appearing in the center of the helix was the element tellurium, so he named his creation ‘the telluric helix’, sometimes also called ‘the telluric spiral’.
Despite the odd choice to name the entire system for a single element, de Chancourtois was onto something here. But even setting the name aside, there was an important drawback to his design.
The position of elements on the helix are not evenly spaced. Instead, their position is proportional to their atomic mass. This causes some elements with similar properties to appear in different regions of each turn. There were hints of periodic order in his spiral, but it did not rigorously preserve all the known information about similarities.
John Newlands’ Rule of Octaves
Meanwhile, just across the English Channel, a chemist by the name of John Newlands tried a different approach, giving each of the known elements a rank number, based on their atomic masses. No one knew about the noble gases, so his numbers were different from modern atomic numbers. But this gave him 1 for Hydrogen, 8 for Fluorine, 15 for Chlorine.
And by lining these elements up and wrapping the list every eighth element, he produced a table of seven columns with eight rows, where the properties seemed to have a tendency to repeat every seventh element. Newlands called his observation the ‘rule of octaves’, likening the columns of his table to octaves of musical notes.
Other scientists could see no scientific basis for his proposed ordering.
A more serious problem was that further along on his table, he took the liberty of placing multiple elements in the same space. For example, cobalt and nickel were forced into a single shared location at position 22.
Even worse, Newlands also seemed to ignore the fact that new elements were still being discovered at a fairly steady rate at this time. Yet his table left no room for any future discoveries!
For all the things it got wrong, though, Newlands’ table did make one big advance from the helix. The elements’ positions in his table were based on the integer rank of their atomic masses, rather than the magnitude of the measured value of their atomic masses.
The Inspiring Karlsruhe Conference
Meanwhile, the sharing of the world’s most up-to-date information about the mass and other properties of elements at Karlsruhe inspired two more chemists to offer an arrangement of the elements that became far more influential.
The German chemist, named Lothar Meyer, produced an initial version of his own table for 28 of the known elements. This was in 1862. Just like Newlands’ table, Meyer ranked elements by atomic weight. But Meyer also realized that it was highly unlikely that all elements were already known at the time.
So his principle for grouping the elements was to go strictly by the ratio in which they combined with other known elements; that’s the valence. This reliance on valence not only allowed for new elements, it actually required creating some empty spaces that allowed new elements to be discovered and added without disrupting existing alignments.
The Russian chemist, Dmitri Mendeleev, took essentially the same idea even further. He took to creating a table of the elements in much the same way that Meyer had, but went far beyond Meyer’s initial effort by attempting to include all 63 known elements.
Common Questions about How the Karlsruhe Conference Influenced Modern Chemistry
The Karlsruhe Conference was the first international chemical conference. Its aim was to get everyone to agree on a uniform system of measuring and reporting experimental results. In addition to notation and nomenclature, one of the prominent issues that was discussed was how best to measure and report on atomic weights.
The Karlsruhe Conference inspired many scientists worldwide to propose their arrangement of the elements. Béguyer de Chancourtois’ telluric helix, John Newlands’ rule of octaves, Dmitri Mendeleev and Lothar Meyer’s tables were among the significant consequences accomplished right after the conference.
Telluric helix was the first periodic arrangement of elements that appeared after the Karlsruhe Conference. Created by the French geologist Béguyer de Chancourtois, it was not a table but a three-dimensional helix. Since the element tellurium was located in the center, de Chancourtois called it ‘the telluric helix’.
