Who can we attribute the modern Periodic System to?

The Periodic System has evolved throughout history, being adapted by many chemists but who can we attribute this vital concept to? Some may suggest Dmitri Mendeleev, as he drew together many theories to produce one resembling what scientists use today. Others may suggest John Newlands or Johann Dobereiner because they attempted organise the elements by properties before Mendeleev. Lastly, it may be suggested that those who came after Mendeleev have developed the Periodic System to focus on atomic numbers not weights, making their contributions more important. So, was it the early discoveries? Mendeleev’s System? Or the modern developments? Early attempts to organise the elements came from John Newlands and Johann Dobereiner. Dobereiner saw that the elements could be grouped into four groups of threes, which he called triads. These would later be seen as vertical columns in the Periodic Table. As such the triads are considered the first step to the Periodic Table. After this, Newlands observed the similarities between elements with atomic weights that differed by seven and attempted to organise the elements this way. Due to this discovery, and that it was produced four years before Mendeleev’s, some scientists (including Newlands) argue that he produced a rudimentary periodic table that would have influenced or preceded Mendeleev’s. This isn’t strictly true as Mendeleev wouldn’t have come across Newland’s discovery. The Royal Society of Chemistry (RSC) refused to publish his paper as his pattern never fit every element. This meant that Mendeleev would never have seen Newlands’ research so it couldn’t contribute to Mendeleev’s theory. The next development came from Mendeleev in 1869. He attempted to sort the elements as Dobereiner and Newlands had, in increasing atomic mass, and noticed that certain types of elements occurred regularly. However, his development differed from theirs as Mendeleev’s wasn’t a rigid pattern. When he noticed a discrepancy in the pattern, he moved the element or left gaps, for example iodine and tellurium were swapped to where we see them today. This shows that Mendeleev was thinking distinctly. However, later discoveries supported his theory. For example the discovery of the inert noble gases in the 1890s by William Ramsay, completing the modern table. Therefore, whilst Mendeleev did develop the theory of the modern Periodic System, later contributions helped to uphold his idea. Overall, Mendeleev started a chain of ongoing discoveries as, without him, it could have been decades until a rudimentary Periodic Table was created and the subsequent discoveries were understood. Six years after Mendeleev’s death Henry Moseley revealed why some of the elements needed to be swapped when arranged by atomic mass as he found a way to accurately measure atomic number using X-rays. This breakthrough allowed scientists to explain why Mendeleev’s observations occurred and led to the creation of a periodic table organised by ascending atomic number. However, Moseley didn’t go any further because he was killed in World War One. Whilst this shows that modern developments can allow us to understand the periodic system, like atomic structure and electron orbitals, Moseley didn’t progress past this. Moreover, the understanding we can obtain from Mendeleev’s observations are an integral part of our understanding of the fundamentals of chemistry. Likewise the later additions to the Periodic Table only serve as further proof of Mendeleev’s theory so they can never be as significant as the original discovery. Therefore, the later discoveries, whilst furthering the field of chemistry in other ways, don’t contribute as much to the understanding of the Periodic System that Mendeleev developed. To conclude, I believe that Mendeleev enabled the evolution and recognition of the Periodic System. This is evident as he was the first to properly understand that there must have been undiscovered elements (so left gaps instead of assuming he knew all the elements). However, it is crucial to note, that I haven’t detailed other scientists who drew similar conclusions to Newlands, Dobereiner and Mendeleev like Meyer and Lavoisier. This is vital because we must appreciate that chemists’ understanding of the Periodic System is ever changing and, throughout history, there were others who drew similar conclusions but didn’t arrive at the structure that Mendeleev did. These scientists deserve recognition whilst not disregarding Mendeleev’s vital contributions to understanding the Periodic System.