This post was written by Science Reference Specialist Nate Smith.
This year marks the 150th anniversary of one of the most important breakthroughs in the field of chemistry: the Periodic Table of Elements. While there have been over 700 distinct iterations of the table (Scerri, 20), the first tables that explicitly showed periodicity were created in the 1860’s.
The first came in 1862 from French geologist Alexandre Emile Béguyer de Chancourtois in the form of his Telluric Screw. According to the Royal Society of Chemistry, his system “plotted the atomic weights of the elements on the outside of a cylinder, so that one complete turn corresponded to an atomic weight increase of 16” (such as Potassium at 39 and Manganese at 55). The overall shape is reminiscent of a candy cane or a barber’s pole.
In 1863, another table showing periodicity was published by English chemist John Newlands. From 1863 to 1890 Newlands published sixteen articles explaining different classifications for the elements, although he is most known today for his law of octaves. This classification placed sixty-five elements into groups based on similar chemical properties, which coincided with repetitions of properties at intervals of eight. Newlands was also the first to place tellurium and iodine in the table based on chemical properties alone instead of the typical method of increasing atomic weight. (Scerri, 76)
In 1864, the same year that Newlands published one of this tables, another English chemist by the name of William Odling published his table showing periodicity of the elements. His was based on chemical properties as well and divided forty-nine elements into thirteen distinct groups. To his credit, Odling, arranged his table purely by chemical properties “without considering atomic weight.” (Morris, 155) Also, he was able to “correctly group lead, mercury and platinum, something that his contemporaries missed.” (Still, 11)
Gustavus Hinrichs, while known for a variety of reasons, including coining the term “derecho,” also created a unique periodic table based on the relationship of what he called “pantogens, with its atoms called panatoms, which explains the numerical relations of atomic weights and gives a simple classification of the elements.” This classification system culminated in 1867 in his spiral periodic table, which better clarified the groupings of elements. Hinrichs’s classification, while distinctly different from the other periodic tables of this period, “seems to capture many of the primary periodicity relationships seen in the modern periodic table…it is not cluttered by attempts to show secondary kinship relationships.” (Scerri, 92)
Yet another chemist who is given credit for independently creating the periodic table of elements is Julius Lothar Meyer. Lothar Meyer published a book in 1864 that contained a table of twenty-eight elements arranged into “six families by order of their valence.” (Still, 14) This table clearly showed a periodic relationship between the elements, though it did not predict the chemical properties of undiscovered elements.
This brings us to the periodic table of this era that is most widely known and accepted as the first (and serves as the basis of this year’s anniversary): Dmitry Ivanovich Mendeleyev’s table of 1869. In writing a new textbook on chemistry, he sought out a way to order the elements. He began by writing each element on a note card along with its atomic weight and chemical properties. Mendeleyev then ordered them into seven groups, while making adjustments based on properties as opposed to atomic weight, or what was thought to be the atomic weight at the time. For instance, uranium was thought to have an atomic weight of 120, but for it to fit into a group with similar properties the weight would need to be 240. Unperturbed, Mendeleyev assigned uranium this atomic weight, which turns out not to be too far from the modern figure of 238. (Morris, 166) The main leap forward caused by this table was that it “not only had the ability to predict the existence of new elements, but also how they might be found. The patterns predicted how elements react with other chemicals, which was the key to unlocking their discovery.” (Still, 13-14)
As humans, we have an innate ability to discover patterns in the world around us. All six of these scientists independently found periodicity in the known elements of their time. The table has drastically changed in the past 150 years; according to Science News, the modern form of the table that we know and love today “became widely popular only after World War II, largely due to the work of the American chemist Glenn Seaborg.” The table has remained relatively fixed in recent decades, but the potential for further change is as limitless as human imagination and ingenuity.
To learn more about the scientists discussed above, a good place to begin is with the following resources:
- Richard Morris – The Last Sorcerers: The Path from Alchemy to the Periodic Table
- Eric R. Scerri – The Periodic Table: Its Story and Its Significance
- Eric R. Scerri and Guillermo Restrepo, eds – Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table
- Ben Still – The Secret Life of the Periodic Table: Unlocking the Mysteries of All 118 Elements
- Paul Strathern – Mendeleyev’s Dream: The Quest for the Elements
And for a fun read about a variety of elements, I highly recommend The Disappearing Spoon by Sam Kean.