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150 Years of the Periodic Table

March 11, 2019

At the corporate research center where I spent most of my career, there were many research laboratories. Some of these were physics laboratories, and some were chemistry laboratories. You knew when you were in a physics laboratory by the abundance of electronic instrumentation, sometimes arranged at the periphery of a large optical table. The chemistry labs were identifiable mostly by their odor, organic labs having a background solvent smell, and inorganic labs mostly reeking of nitrates and sulfates. There was also the incessant roar of fume hoods in the chemistry labs. My materials science laboratory was a composite of these two types with the addition of some very high temperature furnaces.

Nearly every laboratory, whether physics or chemistry, was sure to have at least one item hanging on the wall - the periodic table of the elements. While the element boxes of the periodic tables in the chemistry labs would contain information useful to chemistry, such as atomic weight, valence, and density, the tables in other labs might have such information as the electron binding energy, which is useful for x-ray photoelectron spectroscopy, and crystal structure.

This year, the 150th anniversary of the periodic table, has been proclaimed the International Year of the Periodic Table of Chemical Elements (IYPT2019) by the United Nations General Assembly and UNESCO.[1] The Opening Ceremony of IYPT2019 took place at the UNESCO Headquarters in Paris, France, on January 29, 2019. It was in 1869 that Russian chemist, Dmitri Mendeleev (1834-1907), building on many prior years' work by other chemists, notably Antoine Lavoisier (1743-1794), Humphry Davy (1778-1829), John Dalton (1766-1844), and Jacob Berzelius (1779-1848), first organized all the chemical elements known at that time into a periodic table based on atomic weight.

Figure caption

Dmitri Mendeleev (1834-1907). Left image, Mendeleev in a 1861 portrait by Sergey Lvovich Levitsky (1819-1898), a few years before his publication of the periodic table; and, right image, Mendeleev in 1897. Both images via Wikimedia Commons, modified for artistic effect.

Since Mendeleev could only be guided in creation of his table by the progression of atomic weights and similarities of chemical properties such as valence, there were several errors in his original table. The most glaring of these was the inclusion of the supposed element, didymium, which turned out to be a mixture of the actual elements, praseodymium and neodymium. This happened because these elements, members of the so-called rare earths, are notoriously difficult to chemically separate.

The discovery of quantum mechanics finally gave us the principle that defines the similarities and differences between chemical elements. Electrons were found to populate "shells" of increasing principal quantum number around nuclei of different proton number. These shells have subshells, designated s, p, d, and f, that are populated in the following order that gives the periodic table its block shape:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p.

The electron configuration of the first d-electron metal, scandium, is

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d1, 4s2,

while that of the first f-electron metal, cerium, is

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f1, 5d1, 6s2.

Periodic Table of the Elements
Scientists of all specialties are familiar with the periodic table of the elements. Most of the higher atomic number elements are known to just chemists and materials scientists. Much of my research involved the rare earth elements, so I've personally done experiments with 76 of the elements. One of my wife's inorganic chemistry professors said that he was asked at his dissertation defense to write on a blackboard, from memory, as much of the periodic table as he remembered. (A composite of several Wikimedia Commons images. Click for larger image.)

The February 1, 2019, issue of Science is a special issue with the theme, "Periodic Table Turns 150,"[2] While the introduction to the issue, "Setting the table," by Phillip Szuromi is an open access article,[3] the other articles are unfortunately behind a paywall for non-members of the American Association for the Advancement of Science. These include articles entitled, The quest for superheavies, Ordering the elements, Populating the periodic table: Nucleosynthesis of the elements, Electronic structure in the transition metal block and its implications for light harvesting, and Rare earth elements: Mendeleev’s bane, modern marvels.

Fortunately, this lack of open access is balanced by a recent open access article on stellar nucleosynthesis in Physics Today by Stan Woosley, a professor of astronomy and astrophysics at the University of California, Santa Cruz, Virginia Trimble, a professor of physics and astronomy at the University of California, Irvine, and Friedel Thielemann, a professor emeritus of theoretical physics at the University of Basel (Basel, Switzerland).[4] Stellar nucleosynthesis is the process by which chemical elements are created in stars by their fusion reactions.

The universe was chemically uninteresting at its creation, since the only elements present after the temperature had decreased enough to allow the creation of atomic nuclei were hydrogen, helium and lithium. In 1946, British astronomer, Fred Hoyle, proposed the mechanisms of stellar nucleosynthesis, and this theory was refined by Margaret Burbidge, Geoffrey Burbidge, William A. Fowler and Hoyle in a 1957 paper.[5] This paper, known by the shorthand designation, B2FH, is one of the most cited astrophysics papers, presently having 1,323 citations in journals published by the American Physical Society, and 4,276 overall citations as determined by Google Scholar. Fowler shared the 1983 Nobel Prize in Physics.

Man is always pushing beyond the limits of nature; so, where no natural element has been found, synthetic elements have been created. The most interesting example of this is technetium, Tc, atomic number, 43, synthesized in 1936. Technetium plugged a hole that existed in the periodic table between molybdenum (Mo, atomic number, 42) and Ruthenium (Ru, atomic number, 44). While technicium does exist in nature, it has a half-life of just 4.2 million years, about one-thousandths the age of the Earth. That means that only one atom of technetium would remain from more than 10301 atoms that existed at Earth's formation.

There are other naturally occurring elements that were first known only in their synthesis. These are promethium, polonium, astatine, francium, actinium, protactinium, neptunium, and plutonium. There are other elements, those of atomic number 95 and greater, that have such a short lifetime that they are not found in nature and are only obtained through synthesis, as listed in the following table.

Element Symbol Atomic No. Synthesized
Americium Am 95 1944
Curium Cm 96 1944
Berkelium Bk 97 1949
Californium Cf 98 1950
Einsteinium Es 99 1952
Fermium Fm 100 1952
Mendelevium Md 101 1955
Nobelium No 102 1966
Lawrencium Lr 103 1971
Rutherfordium Rf 104 1966
Dubnium Db 105 1968
Seaborgium Sg 106 1974
Bohrium Bh 107 1981
Hassium Hs 108 1984
Meitnerium Mt 109 1982
Darmstadtium Ds 110 1994
Roentgenium Rg 111 1994
Copernicium Cn 112 1996
Nihonium Nh 113 2003
Flerovium Fl 114 1999
Moscovium Mc 115 2003
Livermorium Lv 116 2000
Tennessine Ts 117 2010
Oganesson Og 118 2002

As I wrote in an earlier article (Michael Faraday, October 8, 2018), there's no greater honor for a scientist than to have an element named after him/her. While some scientists have derived this honor indirectly by having an element named after an institution bearing his name, there are sixteen elements that have been directly named to honor seventeen scientists. Curium was named to honor both Marie Sklodowska-Curie and Pierre Curie, einsteinium to honor Albert Einstein), fermium to honor Enrico Fermi, mendelevium to honor Dmitri Mendeleev, rutherfordium to honor Ernest Rutherford, copernicium to honor Nicolaus Copernicus, seaborgium to honor Glenn T. Seaborg, and oganesson to honor Yuri Oganessian.

Glenn T. Seaborg

Chemist, Glenn T. Seaborg, in the laboratory.

Seaborg was awarded the 1951 Nobel Prize in Chemistry for his work on the synthesis and identification of ten transuranic elements.

Seaborg died on February 25, 1999, but element-106, Seaborgium (Sg), was named in his honor in 1997. Russian nuclear physicist, Yuri Oganessian, is the only other person to have an element named for him in his lifetime.

Politics is everywhere, even in the sciences, so Seaborg's honor came as a result of a compromise in the naming of elements 104-108.

(Lawrence Berkeley National Laboratory/United States Department of Energy image, via Wikimedia Commons, modified for artistic effect.)

It will be difficult to create and detect elements beyond atomic number 118, since their lifetimes are predicted to be far less than a second. The next element, the element with atomic number 119, would be placed below francium in the periodic table, and it's predicted to have chemical properties similar to the other Group 1 elements, the alkali metals such as sodium (Na) and potassium (K).

'oddball' chemical elements

The "oddball" chemical elements. These are the elements whose symbols don't match their English names. The symbol Na for sodium derives from the Latin word for salt, natrium; potassium (K) from the Latin word for potash, kalium; iron (Fe) from its Latin name, ferrum; silver (Ag) from its Latin name, argentum; tin (Sn) from its Latin name, stannum; antimony (Sb) from the Latin name for its mineral, stibium; tungsten (W) from the German name of its mineral, wolframite; gold (Au) from its Latin name, aurum; mercury (Hg) from its Latin and Greek names, hydrargyrum and 'υδραργυρος (hydrargyros, silver water); and, lead (Pb) from its Latin name, plumbum. (Created using Inkscape)

Theodore Gray, one of the founders of Wolfram Research, and founder of Touch Press, a company creating educational apps that included one on the chemical elements, has built an actual table with compartments containing specimens of nearly all the elements (the radioactive and short lifetime ones are absent). Shown below is the dysprosium compartment of his Periodic Table Table. Dysprosium is used to form the highly magnetostrictive alloy, Terfenol-D, Tb0.3Dy0.7Fe2.

Theodore Gray and a compartment from his Periodic Table

Theodore Gray and the dysprosium compartment from his Periodic Table Table. I wrote about Gray in an earlier article (The Periodic Table Table, April 17, 2012). (Left and right images, screen captures from a YouTube video.[6]


  1. The International Year of the Periodic Table - A Common Language for Science, iypt2019 Website.
  2. Special Issue - Periodic Table Turns 150, Science, Science, vol. 363, no. 6426 (February 1, 2019).
  3. Phillip Szuromi, "Setting the table," Science, vol. 363, no. 6426 (February 1, 2019), pp. 464-465, DOI: 10.1126/science.aaw6790.
  4. Stan Woosley, Virginia Trimble, and Friedel Thielemann, "The origin of the elements," Physics Today, vol. 72, no. 2 (February, 2019), pp. 36-37, https://doi.org/10.1063/PT.3.4134.
  5. E. Margaret Burbidge, G. R. Burbidge, William A. Fowler, and F. Hoyle, "Synthesis of the Elements in Stars," Rev. Mod. Phys., vol. 29, no. 4 (October 1, 1957), pp. 547ff., DOI:https://doi.org/10.1103/RevModPhys.29.547.
  6. The Periodic Table Table Featuring Theo Gray, YouTube video by BytesizeScience, February 22, 2012.
  7. Theodore Gray and Nick Mann, "Elements: A Visual Exploration of Every Known Atom in the Universe," Black Dog & Leventhal Publishers, April 3, 2012, 240 pp., ISBN 978-1579128951 (via Amazon).

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