Dmitri Mendeleeff

Dmitri Ivanovich Mendeléeff (born 1834, died 1907; photograph below right→↓) as born in Tobol'sk in western Siberia, the youngest child of a very large family (some report 14 to 17 children).  His maternal grandparents had established the first glassworks and paper mill in Tobol'sk.  While still young, Dmitri's father lost his job as director of the Tobol'sk gymnasium due to cataracts in both eyes.  To provide for the family his mother, Maria, founded and successfully managed her own glassworks in a neighboring village.  Dmitri excelled in mathematics, physics, and history.  He graduated from the gymnasium shortly after his father died of tuberculosis and the glassworks burned to the ground.  Maria secured horses and journeyed the great distance to Moscow with her two youngest children, hoping to enroll Dmitri in University.  Failing to do so, she continued to Petrograd (now St. Petersburg) where a friend of her late husband arranged for Dmitri to begin work in the department of physics and mathematics at the Central Pedagogic Institute.  A few months later Maria also died.  When dying, she said Refrain from illusions, insist on work, and not on words.  Patiently search divine and scientific truth.

When Mendeléeff graduated from the Pedagogical Institute, he received a gold medal for excellence in scholarship.  In his undergraduate thesis on mineral analysis he compiled and systematized large amounts of chemical data and began considering the problem of similarity of substances.  Between 1859 and 1861 he worked with Regnault in Paris and Bunsen in Heidelberg.  The instruments he purchased in Western Europe enabled him to measure the properties of substances with very good precision.  He too attended the first International Chemical Congress in September 1860 at Karlsruhe and had been impressed by the paper on determining atomic weights Stanislao Cannizzaro distributed.  Mendeléeff immediately wrote his teacher in Petrograd (which was publish in a Petrograd newspaper and a Moscow journal) noting that Cannizzaro corrected inconsistencies in existing atomic weights of metals so that atomic heats divided by a substance's number of atoms resulted in a constant (about 6 to 7) in accord with Dulong and Petit.  Before returning to Russia he visited the new oil fields in Pennsylvania.  Upon his return to Petrograd in early 1861, he was granted his doctorate and appointed professor of chemistry at the Technological Institute.  His doctoral thesis was On Compounds of Alcohol with Water.  Now teaching, he completed his first chemistry textbook, Organic Chemistry.  It was well received and in 1862 he received the Demidov Prize for the outstanding book.

In the Fall of 1867 he became professor of general chemistry at the University of Petrograd.  Not finding any suitable Russian textbook to recommend to students, he began to write The Principles of Chemistry, the first portion which was published in May or June 1868.  Mendeléeff searched for an organizing principle so that the mass of chemical knowledge would not be chaotic.  While the law of definite chemical compounds had persuasively proven the atomic theory, a whole group of so-called indefinite compounds and solutions seemed to refute the atomic theory.  Distinct chemical elements with well defined atomic weights clearly existed, but the actual existence and nature of atoms was more problematic.  On February 17, 1869 he completed his first periodic table which in March he presented as a paper to the Russian Chemical Society on The Relation of the Properties to the Atomic Weights of the Elements.  He fell ill just before the meeting so he had N.A.Menshutkin read it aloud for him.  In this paper he presented a periodic table, boldly noted the periodic relationship of chemical formulas to atomic weights, noted some elements had atomic weights that needed correction, and forecast that new elements would be discovered to fit vacant spaces in his table.  The same month Mendeléeff published the second volume of The Principles of Chemistry, Chapters 12-22.  Paradoxically, it appears Mendeléeff found the weight of elements was an invariable characteristic that provided an organization for studying chemistry free from employing the notion of atoms which remained shrouded in controversy.

The paper included eight conclusions including:

The properties of the elements show a periodic change with increasing atomic weight.

Most common elements in nature have low atomic weights.

The three elements (those right of Aluminum and Silicon, and below Calcium) are required but not yet discovered.

Several atomic weights appear to be in error and need correction.

At the end of March 1970 the third volume was published and the final two volumes were published in February 1871.  In July 1871 Mendeléeff published a comprehensive paper on the periodic law.  But it was in February 1869 that Mendeléeff first realized that atomic weights, not valence should be the guiding principle for chemistry.  In subsequent editions, eight in all, he significantly revised the structure of the textbook to be in more accord with the periodic law with each new edition.

In 1871 Mendeléeff produced a form of the periodic chart horizontal like Meyers, predicted atomic weights for nine missing elements, and gave detailed predictions of the properties for eka-Boron, eka-Aluminum, and eka-Silicon.

In 1871 Mendeléeff left blanks for 32 missing elements.

Unlike the traditional elements which provided a wealth of properties to organize, only a few of the rare earths were known making interpolation of their number and properties difficult.  Besides eka Cs and eka Nb above, there were a number of the 32 predicted elements that Mendeléeff predicted in error.  In 1889 Mendeléeff predicted details for dwi Te which was discovered in 1898 and called Polonium by the Curies.

Despite Mendeléeff's believe that some atomic weights were in error, more careful measurements of Ar (39.95) and K (39.10), Co (58.93) and Ni (58.69), and Te (127.6) and I (126.91) left them inverted with the heavier element in each pair preceding the lighter.  (Understanding that would require knowledge of the nucleus which wouldn't even be discovered until the next century.  At right Mendeléeff is pictured at work in his study.)

The establishment of the periodic system was regarded by most chemists as a discovery of the highest importance.  Stanislao Cannizzaro had provided the key to establishing atomic weights with Avogadro's hypothesis.  A number of chemists had found patterns in those weights.  Mendeléeff had recognized the periodic table's broad power to organize all that was know about the chemical elements and their compounds plus the value for predicting yet undiscovered substances and their properties.  Meyers had first used the pattern to merely suggest the difficulty with simple atoms but quickly appreciated and popularized the broad significance suggested by Mendeléeff.  Alexandre Emile Béguyer de Chancourtois (b1820, d1886), professor of geology at the École des Mines in Paris, described to the French Academy of Sciences in 1882-3 his vis Tellurique (earthy screw) plotting atomic weights on a helix with 16 atomic mass units per turn.  (However Chancourtois' screw does NOT align any chemical families; he found no chemical periodicity.)  William Odling (b1829, d1921), a reader in chemistry at St. Bartholomew's Hospital in London had suggested an arithmetical seriation of atomic weights in 1864.  Gustavus Detlef Hinrichs (b1836, d1923), professor at the University of Iowa, published in 1867 a radial periodic chart with each family arranged along spokes with the monomer of all atoms, an Urstoff called pantogen with a weight of half hydrogen's at the center.  (But only non-metals had arcs of similar atomic weights.)  So it was Mendeléeff's broad appreciation for the significance and practical use of the periodic law for all elements that won him acknowldgement as its discoverer.

But the failure to immediately find the expected underlying unity of matter implied by the periodic table became frustrating to many chemists.  No Urstoff was found, yet there must be an explanation why the properties of elements reoccurred periodically.

In 1904, Mendeléeff extrapolated two elements lighter than Hydrogen, and several heavy elements.  Few of those predictions were accurate.

Primary Information Sources:

• Aaron J. Ihde, The Development of Modern Chemistry, Dover, 1964 & 1984
• William B. Jensen, Lecture on the Discovery of the Periodic Law, Beckman Center for the History of Chemistry, July 1991
• Masanori Kaji, D.I. Mendeleev's Concept of Chemical Elements and the Principles of Chemistry, Bulletin for the History of Chemistry, vol. 27, #1, 2002
• Edward G. Mazurs, Graphic Representatations of the Periodic System During One Hundred Years, U. Alabama Press, 1974
• Mary Elvira Weeks, Discovery of the Elements, Journal of Chemical Education, 1945

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created 23 March 2002, additions 1 April latest revision 26 April 2010

by D Trapp