Dmitri Mendeleev
Dmitri Ivanovich Mendeleev was a Russian chemist known for formulating the periodic law and creating a version of the periodic table of elements. He used the periodic law not only to correct the then-accepted properties of some known elements, such as the valence and atomic weight of uranium, but also to predict the properties of three elements that were yet to be discovered. The synthetic element Mendelevium is named in his honor.
Early life
Mendeleev was born in the village of Verkhnie Aremzyani, near Tobolsk in Siberia, to Ivan Pavlovich Mendeleev and Maria Dmitrievna Mendeleeva . Ivan worked as a school principal and a teacher of fine arts, politics and philosophy at the Tambov and Saratov gymnasiums. Ivan's father, Pavel Maximovich Sokolov, was a Russian Orthodox priest from the Tver region. As per the tradition of priests of that time, Pavel's children were given new family names while attending the theological seminary, with Ivan getting the family name Mendeleev after the name of a local landlord.Maria Kornilieva came from a well-known family of Tobolsk merchants, founders of the first Siberian printing house who traced their ancestry to Yakov Korniliev, a 17th-century posad man turned a wealthy merchant. In 1889, a local librarian published an article in the Tobolsk newspaper where he claimed that Yakov was a baptized Teleut, an ethnic minority known as "white Kalmyks" at the time. Since no sources were provided and no documented facts of Yakov's life were ever revealed, biographers generally dismiss it as a myth. In 1908, shortly after Mendeleev's death, one of his nieces published Family Chronicles. Memories about D. I. Mendeleev where she voiced "a family legend" about Maria's grandfather who married "a Kyrgyz or Tatar beauty whom he loved so much that when she died, he also died from grief". This, however, contradicts the documented family chronicles, and neither of those legends is supported by Mendeleev's autobiography, his daughter's or his wife's memoirs. Yet some Western scholars still refer to Mendeleev's supposed "Mongol", "Tatar", "Tartarian" or simply "Asian" ancestry as a fact.
Mendeleev was raised as an Orthodox Christian, his mother encouraging him to "patiently search divine and scientific truth". His son Ivan would later inform that Mendeleev had departed from the Church and embraced a form of "romanticized deism".
Mendeleev was the youngest of 17 siblings, of whom "only 14 stayed alive to be baptized" according to Mendeleev's brother Pavel, meaning the others died soon after their birth. The exact number of Mendeleev's siblings differs among sources and is still a matter of some historical dispute. Unfortunately for the family's financial well-being, his father became blind and lost his teaching position. His mother was forced to work and she restarted her family's abandoned glass factory. At the age of 13, after the passing of his father and the destruction of his mother's factory by fire, Mendeleev attended the Gymnasium in Tobolsk.
In 1849, his mother took Mendeleev across Russia from Siberia to Moscow with the aim of getting Mendeleev enrolled at the Moscow University. The university in Moscow did not accept him. The mother and son continued to Saint Petersburg to the father's alma mater. The now poor Mendeleev family relocated to Saint Petersburg, where he entered the Main Pedagogical Institute in 1850. After graduation, he contracted tuberculosis, causing him to move to the Crimean Peninsula on the northern coast of the Black Sea in 1855. While there, he became a science master of the 1st Simferopol Gymnasium. In 1857, he returned to Saint Petersburg with fully restored health.
Between 1859 and 1861, he worked on the capillarity of liquids and the workings of the spectroscope in Heidelberg. Later in 1861, he published a textbook named Organic Chemistry. This won him the Demidov Prize of the Petersburg Academy of Sciences.
On 4 April 1862, he became engaged to Feozva Nikitichna Leshcheva, and they married on 27 April 1862 at Nikolaev Engineering Institute's church in Saint Petersburg.
Mendeleev became a professor at the Saint Petersburg Technological Institute and Saint Petersburg State University in 1864, and 1865, respectively. In 1865, he became a Doctor of Science for his dissertation "On the Combinations of Water with Alcohol". He achieved tenure in 1867 at St. Petersburg University and started to teach inorganic chemistry while succeeding Voskresenskii to this post; by 1871, he had transformed Saint Petersburg into an internationally recognized center for chemistry research.
Periodic table
In 1863, there were 56 known elements, with a new element being discovered at a rate of approximately one per year. Other scientists had previously identified periodicity of elements. John Newlands described a Law of Octaves, noting their periodicity according to relative atomic weight in 1864, publishing it in 1865. His proposal identified the potential for new elements such as germanium. The concept was criticized, and his innovation was not recognized by the Society of Chemists until 1887. Another person to propose a periodic table was Lothar Meyer, who published a paper in 1864 describing 28 elements classified by their valence, but with no predictions of new elements.After becoming a teacher in 1867, Mendeleev wrote Principles of Chemistry, which became the definitive textbook of its time. It was published in two volumes between 1868 and 1870, and Mendeleev wrote it as he was preparing a textbook for his course. This is when he made his most important discovery. As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his periodic table; he claimed to have envisioned the complete arrangement of the elements in a dream:
Unaware of the earlier work on periodic tables going on in the 1860s, he made the following table:
| Cl 35.5 | K 39 | Ca 40 |
| Br 80 | Rb 85 | Sr 88 |
| I 127 | Cs 133 | Ba 137 |
By adding additional elements following this pattern, Mendeleev developed his extended version of the periodic table. On 6 March 1869, he made a formal presentation to the Russian Chemical Society, titled The Dependence between the Properties of the Atomic Weights of the Elements, which described elements according to both atomic weight and valence. This presentation stated that
- The elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties.
- Elements which are similar regarding their chemical properties either have similar atomic weights or have their atomic weights increasing regularly.
- The arrangement of the elements in groups of elements in the order of their atomic weights corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, B, C, N, O, and F.
- The elements which are the most widely diffused have small atomic weights.
- The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body.
- We must expect the discovery of many yet unknown elements – for example, two elements, analogous to aluminium and silicon, whose atomic weights would be between 65 and 75.
- The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128.
- Certain characteristic properties of elements can be foretold from their atomic weights.
Mendeleev also proposed changes in the properties of some known elements. Prior to his work, uranium was supposed to have valence 3 and atomic weight about 120. Mendeleev realized that these values did not fit in his periodic table, and doubled both to valence 6 and atomic weight 240.
For his predicted three elements, he used the prefixes of eka, dvi, and tri in their naming. Mendeleev questioned some of the currently accepted atomic weights, pointing out that they did not correspond to those suggested by his Periodic Law. He noted that tellurium has a higher atomic weight than iodine, but he placed them in the right order, incorrectly predicting that the accepted atomic weights at the time were at fault. He was puzzled about where to put the known lanthanides, and predicted the existence of another row to the table which were the actinides which were some of the heaviest in atomic weight. Some people dismissed Mendeleev for predicting that there would be more elements, but he was proven to be correct when Ga and Ge were found in 1875 and 1886 respectively, fitting perfectly into the two missing spaces.
By using Sanskrit prefixes to name "missing" elements, Mendeleev may have recorded his debt to the Sanskrit grammarians of ancient India, who had created theories of language based on their discovery of the two-dimensional patterns of speech sounds. Mendeleev was a friend and colleague of the Sanskritist Otto von Böhtlingk, who was preparing the second edition of his book on Pāṇini at about this time, and Mendeleev wished to honor Pāṇini with his nomenclature.
The original draft made by Mendeleev would be found years later and published under the name Tentative System of Elements.
Dmitri Mendeleev is often referred to as the Father of the Periodic Table. He called his table or matrix, "the Periodic System".