I'm Trying to Understand How the Modern Table of Elements Came to Be
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| GeeksforGeeks |
Mendeleev was far from the first chemist to attempt to organize the elements by atomic weight or to recognize that characteristics recurred on some sort of regular basis. Through much of the nineteenth century, chemists had worked to find an organizing principle that encompassed all of the known elements and that could be considered a law of nature.Mendeleev’s system was not perfect but it had the hallmarks of a scientific law, one that would hold true through new discoveries and against all challenges.One of the unique aspects of Mendeleev’s table was the gaps he left. In these places he not only predicted there were as-yet-undiscovered elements, but he predicted their atomic weights and their characteristics. The discovery of new elements in the 1870s that fulfilled several of his predictions brought increased interest to the periodic system and it became not only an object of study but a tool for research.
Then we had the discovery of the noble gases:
In the 1890s, William Ramsay discovered an entirely new and unpredicted set of elements, the noble gases. After uncovering the first two, argon and helium, he quickly discovered three more elements after using the periodic system to predict their atomic weights. The noble gases had unusual characteristics—they were largely inert and resistant to combining with other substances—but the entire set fit easily into the system.
The discovery of radioactivity in 1896 seemed poised to destroy the periodic system. Chemists had always considered elements to be substances that could not break down into smaller parts. How could radioactive elements, which decayed into other substances, be considered elements? And if they were, how could so many fit into the very few gaps left in the table?
Chemists and physicists working together began to understand the structure of the atom and were soon able to explain how the periodic system worked on an atomic level.
This is a very interesting note in what was in the mind of Mendeleev when he invented the periodic table:
Mendeleev and many of the others who developed systems to organize the elements did so in their roles as chemical educators rather than as chemical researchers. He was writing a textbook for his students at St. Petersburg University (the only available chemistry textbooks in Russian were translations) when he developed his periodic law. Perhaps most important, he continued to draw revised versions of the periodic table throughout his life.
Neither Mendeleev’s first attempt at the periodic system nor his most popular table from 1870 look much like the periodic table that hangs today on the wall of most chemistry classrooms or appears inside the cover of most chemistry textbooks. Now, there are probably 1,000 different periodic tables of the elements.
Later on, we have another important person from where we get the modern periodic table:
There were so many similar tables that in some ways it just evolved over time. But chemists frequently point to the table created by Horace G. Deming, a professor at the University of Nebraska, as the progenitor. Deming’s table first appeared in his 1923 textbook General Chemistry and was slightly modified in each edition until the final one appeared in 1952.
Chemical educators lauded Deming’s table, but scientific supply companies made it famous. Merck handed it out as part of a promotional campaign in the 1920s. The Welch Scientific Company sold it in the form of wall charts, and in standard page size and vest pocket editions.
Eventually it was included in standard reference handbooks such as the CRC Handbook of Chemistry and Physics and Lange’s Handbook of Chemistry. By the 1950s, versions of Deming’s table could be found in a majority of chemistry textbooks.
From the Science Connected Magazine, here's an interesting summary of how the periodic table came to be:
While the information about each element in the Periodic Table is the same, different formats have been used to organize the Periodic Table. The Periodic Table has also evolved. Let us take a brief look at both the history and the most common versions in use today.
John Newlands organized elements based on weights. He observed there were similar properties every eight elements, so he organized his table with eight columns. He left no gaps in his table.
In 1863 Dmitri Mendeleev drafted the first of his 60 versions of the Periodic Table. He used atomic weights to sort the elements; however, he reordered them based on observed properties if they did not seem to be in the right spots. This was accurate, although speculative. Mendeleev trusted experimental evidence of chemical reactions more than the measured weights. He was correct because many elements were difficult to isolate in the samples at the time. Frequently incorrect weights were reported and later revised when purer samples could be analyzed.
Mendeleev left gaps where there was no known element matching the anticipated weight and properties. Mendeleev’s gap for Gallium (Eka-Aluminium) is a well-known example. By 1871 Mendeleev had a Periodic Table in eight groups related to oxidation states. This 8-column format was used for decades, even after other formats were developed.
Skipping ahead to 1913, Anton van den Broek, proposed the nuclear charge determined the placement in the Periodic Table. In 1914 Johannes Rydberg determined a relationship in the atomic numbers of noble gases. This led to the octet rule and valence bond theories. This was further adapted into the Bohr model. Combined with Pauli’s exclusion principle a quantum rule for filling electron shells was determined. Finally, Glenn Seaborg proposed the f-series (Actinide Series) based on his research on Americium and Curium.
“I believe that the chief difference is that you [Glenn Seaborg]are using the periodic table to express the probable configuration of the electron shells, while I and a few other chemists are primarily concerned with the representation of the chemical character of the elements.” – F.A.Paneth to G.T.Seaborg, 14 July 1950, Box 342, Glenn Theodore Seaborg Papers, Manuscript Division, Library of Congress, Washington, D.C.; c.f. Doctoral Dissertation, Creating a Symbol of Science: The Development of a Standard Periodic Table of the Elements Ann Robinson, p. 247
The discovery of many more elements than originally in Mendeleev’s Table, increased understanding of the nucleus (protons and neutrons), as well as electron orbitals, led to the modern Periodic Table.
There were several forms of the Periodic Table used in textbooks in the 1950s. Some were 8-column, 18-column, and 32-column tables. Others were arrangements referred to as “rocket ships,” based on Niels Bohr’s early Periodic Tables.
Today’s most used version of the Periodic Table evolved from Horace G. Deming’s 1923 General Chemistry textbook. It contains 18 columns and is itself derived from Alfred Wagner’s 1905 18-column “block” layout reflecting the s-, d-, and p-blocks (sub-shells) [1]. The long version with the f-block “inline” has 32 columns.
Deming’s table achieved a breakthrough in 1928 because the publisher distributed U.S. letter-size printouts as part of a promotional campaign. These continued to be provided with new editions for several decades. The wide distribution of these materials in Western countries and the practical format led to this 18-column form becoming the most popular version.
The 18-column version of the Periodic Table is not superior to other versions. Indeed the 32-column format has multiple advantages; however, it has a significant disadvantage: layout space. The 18-column version is more compact with a favorable aspect ratio allowing it to fit easily on textbook pages or handouts. The 32-column format requires foldouts or much longer printed charts. Even in our digital world, aspect ratios on web pages and computer monitors or smartphones typically favor the 18-column design.
In summary, there is no official version of the Periodic Table approved by the International Union of Pure and Applied Chemistry (IUPAC) or other bodies. A widely used version of the Periodic Table in 18-column format has been used since the 1950s and can trace its usage back to Deming’s General Chemistry (1923) and even before that to Alfred Wegner’s 1905 “block” layout.
Today’s primary use of the Periodic Table is education. There have been adaptations to reflect various aspects of the elements better: sometimes these focused on chemical characteristics, and sometimes there was focus on physical aspects.
I may not like doing chemistry problems but studying the history of science makes it enjoyable. Sure, it's tedious to try and solve chemistry problems. However, seeing a chemistry exhibit at the University of San Carlos-Talamban Campus (USC-TC) made me see how chemistry is fascinating. We had a brilliant teacher. The problem is once again, the education system. Chemistry, like any subject, can be fascinating or boring, depending on how the education system runs it.
