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CELEBRATING THIS YEAR’S 150th anniversary of Mendeleev’s descriptive array of elements, scientists also discuss modifications to the Period Table. This and other matters arose at the American Chemical Society’s national meeting in San Diego, August 25–29, 2019. Here are tidbits gleaned from Siobhan Roberts’ “Is It Time to Upend the Periodic Table?” The New York Times, August 27, 2019, and other Internet sleuthing.
Mendeleev’s Logical Array. It was February 1869 when Russian chemist Dmitri Mendeleev published his classification of all known elements. Siobhan Roberts writes that his Periodic Table “has been called ‘Nature’s Rosetta Stone,’ ‘the chemist’s map,’ and ‘probably the most compact and meaningful compilation of knowledge yet devised.”
One scientist at the San Diego ACS meeting observed, “If you tell me an element is in a certain place, I can tell you lots of things about it—whether it’s a metal or not, whether it’s abundant on earth or not….” Another said, “If you want to communicate with an alien race, put up a periodic table because that arrangement is universal no matter where you are.”
A + B ≠ A + B. Roberts writes, “Even in the bright light of modern science, chemical reactions remain profoundly captivating.” She cites another scientist noting, “In a physical mixture, you get the sum of the parts when you mix A and B. In chemistry, you combine A and B and you get something qualitatively new.”
An example: The reaction between sodium, a silvery poisonous metal, and chlorine, a green poisonous gas, gives sodium chloride—ordinary salt.
A Plethora of Options. Mendeleev chose a two-dimensional chart arranging the elements by atomic weight. The Internet Database of Periodic Tables lists more than 1000 different possibilities for displaying elemental properties.
One approach is based on elements’ scarcities. Others arrange them in three-dimensional arrays; some in spiral, helical or clocklike arrangements. Whimsically enough, there are also cupcake, Lego, or haiku variations. Roberts also cites Tom Lehrer’s musical version inspired by Gilbert and Sullivan.
Heavy! If Short-lived. Roberts observes, “The heaviest naturally occurring element on the table is uranium, with the atomic number 92 (because it has 92 protons in its nucleus). But the Periodic Table contains still more; the heaviest so far is element 118, oganesson, a ‘super-heavy’ element with 118 protons and a half-life of half a millisecond.”
“Starting in 2020,” she continues, “scientists will attempt to synthesize elements 119 and 120, with a newly inaugurated Superheavy Element Factory….” at the Flerov Laboratory of Nuclear Reactions, in Dubna, Russia. “Their goal,” Roberts writes, is “to reach an ‘island of stability,’ a fabled region of the Periodic Table populated by superheavy elements with greater longevity.”
The Dubna research facility, about 80 miles north of Moscow, is not to be confused with recent revelations of an explosion during Russian nuclear-powered missile testing in Nyonoksa, Arkangelsk Oblast, some 800 miles north of Moscow.
A Modified Periodic Table is Ready. Roberts cites the work of Pekka Pyykkö, a computational chemist at the University of Helsinki. In 2016, he presented a technical paper describing a Period Table classifying elements up to atomic number 172.
That should handle matters for awhile. ds
© Dennis Simanaitis, SimanaitisSays.com, 2019