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Dmitri Mendeleev’s Periodic Table (March 6, 1869)

“There's antimony, arsenic, aluminum, selenium, And hydrogen and oxygen and nitrogen, and rhenium, And nickel, neodymium, neptunium, germanium, And iron, americium, ruthenium, uranium, Europium, zirconium, lutetium, vanadium, And lanthanum and osmium and astatine and radium, And gold and protactinium and indium and gallium, And iodine and thorium and thulium and thallium…” –The Elements, Tom Lehrer

Beyond the first verse of the Tom Lehrer song, most people’s heads start to swim—well, truth be told, half way through the first verse of Tom Lehrer’s song, most people’s heads start to swim! However, the Periodic Table of Elements is an invaluable tool to chemists and students who begrudgingly take the class. This table details not only the scientific name and chemical symbol for the element, but it’s mass, weight, charge, number of valance electrons, family/group, and why is your head spinning in circles?! To say the least, it is a detailed tool that only scratches the molecular surface. But, just how—and who—developed this idea of a periodic table, and what, exactly does it mean?

I’m very glad you asked.

Back in the days of Aristotle, there were only four elements: Earth, Air, Water, and Fire; these four elements could be combined to create each other. Of course, this idea was disproved as scientists (or alchemists, as they were) began discovering elements as we know them today.

To have easy access, there needed to be a “database,” of sorts, to keep track. This database would be known as the Periodic Table. But, I’m jumping ahead. I’ll try not to get too technical, though, admittedly, Chemistry is a love of mine. This concept was first put down prior to any ideas of subatomic particles or quantum mechanics. It was in 1829, when a German chemist named Johann Wolfgang Döbereiner discovered what he called The Law of Triads. He noted that the middle element of the triad possessed the average of the atomic weight of the other two elements in the triad. His discovery laid the ground work for other chemists who realized the relationship extended beyond just triads and into “groups” or “families.”

In 1865, an English chemist, John Newlands, noticed the pattern recurring every eight steps—in other words, when placing elements in order by atomic weight, those elements with similar properties recurred every eighth place. He called this the Law of Octaves--which would have worked, except for the undiscovered Noble Gasses that blew his theory, well, off the chart.

Finally, in 1869, Russian chemist, Dmitri Mendeleev decided to arrange the elements according to mass. By doing this, he was able to predict a pattern of how the elements would line up—a periodicity, so to speak. A few of the elements were taken out of their strict mass-order to couple them with elements that retained similar properties. Some elements had their masses recalculated, and some elements just weren’t discovered at the time—but, Mendeleev was able to predict with striking accuracy how the “missing” elements would react and what their properties would be. Mendeleev presented his findings to the Russian Chemical Society on March 6, 1869. Four months after Mendeleev published his Periodic Table, another chemist—Lothar Meyer—published his findings, which were nearly identical to Mendeleev. The biggest difference between Mendeleev and Meyer was that Mendeleev believed he could predict the mass and weight of the missing elements when arranged as he had done. Meyer did not.

The success of Mendeleev’s Periodic Law helped him to accurately predict the qualities of germanium, gallium, and scandium, thus awarding him the full credit for developing the table as we know it today. When Mendeleev and the others were doing their work and forging pathways in chemistry, there were only about 63 known elements. By 1959, when Tom Lehrer popularized chemistry in song, there were 102 elements. His song even ends with, “These are the only ones of which the news has come to Harvard. There may be many others, but they haven’t been discovered!” As of March 10, 2009, there are 117 elements on the Periodic Table.

To view the sources for this article, please visit the following sites:

Dimitri Mendeleev
The Periodic Table (History)
Element Discoveries
Tom Lehrer’s Song, The Elements

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