Editing Dmitri Mendeleev (section)

==Periodic table==
{{See also|History of the periodic table}}
[[File:Mendelejevs periodiska system 1871.png|thumb|Mendeleev's 1871 periodic table]]
{{sidebar periodic table|history}}
[[File:Periodic table monument.jpg|thumb|Sculpture in honor of Mendeleev and the periodic table, located in [[Bratislava]], Slovakia]]

In 1863, there were 56 known [[Chemical element|elements]], with a new element being discovered at a rate of approximately one per year. Other scientists had previously identified periodicity of elements. [[John Alexander Reina Newlands|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'' ({{langx|ru|Основы химии|translit=Osnovy khimii}}), 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.{{sfn|Heilbron|2003|page=509}} This is when he made his most important discovery.{{sfn|Heilbron|2003|page=509}} 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]]:<ref>John B. Arden (1998). "Science, Theology and Consciousness", Praeger Frederick A. p. 59: "The initial expression of the commonly used chemical periodic table was reportedly envisioned in a dream. In 1869, Dmitri Mendeleev claimed to have had a dream in which he envisioned a table in which all the chemical elements were arranged according to their atomic weight."</ref><ref>John Kotz, Paul Treichel, Gabriela Weaver (2005). "Chemistry and Chemical Reactivity," Cengage Learning. p. 333</ref><ref>Gerard I. Nierenberg (1986). "The art of creative thinking", Simon & Schuster, p. 201: ''Dmitri Mendeleev's solution for the arrangement of the elements that came to him in a dream.''</ref><ref>Helen Palmer (1998). "Inner Knowing: Consciousness, Creativity, Insight, and Intuition".  J.P. Tarcher/Putnam. p. 113: "The sewing machine, for instance, invented by Elias Howe, was developed from material appearing in a dream, as was Dmitri Mendeleev's periodic table of elements"</ref><ref>Simon S. Godfrey (2003). ''Dreams & Reality''. Trafford Publishing. Chapter 2.: "The Russian chemist, Dmitri Mendeleev (1834–1907), described a dream in which he saw the periodic table of elements in its complete form." {{ISBN|1412011434}}</ref>

{{Blockquote|I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary.|Mendeleev, as quoted by Inostrantzev<ref>"[http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=33706 The Soviet Review Translations] {{Webarchive|url=https://web.archive.org/web/20140418233759/http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=33706 |date=18 April 2014 }}" Summer 1967. Vol. VIII, No. 2, M.E. Sharpe, Incorporated, p. 38</ref><ref>Myron E. Sharpe, (1967). "Soviet Psychology". Volume 5, p. 30.</ref>}}

Unaware of the earlier work on periodic tables going on in the 1860s, he made the following table:
{| class="wikitable"
|-
| 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.<ref>"[http://www.wou.edu/las/physci/ch412/perhist.htm A brief history of the development of the period table]", wou.edu</ref><ref>"[http://www.chemsheets.co.uk/GCSEPeriod07.doc Mendeleev and the Periodic Table]" {{webarchive|url=https://web.archive.org/web/20110912072801/http://www.chemsheets.co.uk/GCSEPeriod07.doc |date=12 September 2011 }}, chemsheets.co.uk</ref> 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]] (now called ''relative atomic mass'') and [[valence (chemistry)|valence]].<ref name="Seaborg1994">{{cite book|last=Seaborg|first=Glenn T|author-link=Glenn T. Seaborg|title=Modern Alchemy: Selected Papers of Glenn T Seaborg|chapter-url=https://books.google.com/books?id=573sCgAAQBAJ&pg=PA179|access-date=5 March 2016|date=1994|publisher=World Scientific|isbn=978-9814502993|page=179|chapter=The Periodic Table: Tortuous path to man-made elements}}</ref><ref name="Pfennig2015">{{cite book|last=Pfennig|first=Brian W.|title=Principles of Inorganic Chemistry|url=https://books.google.com/books?id=pxX1BgAAQBAJ&pg=PA109|access-date=4 March 2016|date=2015|publisher=Wiley|isbn=978-1118859025|page=109}}</ref> 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 (e.g., Pt, Ir, Os) or have their atomic weights increasing regularly (e.g., K, Rb, Cs).
# 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. (Tellurium's atomic weight is 127.6, and Mendeleev was incorrect in his assumption that atomic weight must increase with position within a period.)
# Certain characteristic properties of elements can be foretold from their atomic weights.

Mendeleev published his periodic table of all known elements and predicted several new elements to complete the table in a Russian-language journal. Only a few months after, Meyer published a virtually identical table in a German-language journal.<ref name="Nye">{{cite journal|last1=Nye|first1=Mary Jo|title=Speaking in Tongues: Science's centuries-long hunt for a common language|journal=Distillations|date=2016|volume=2|issue=1|pages=40–43|url=https://www.sciencehistory.org/distillations/magazine/speaking-in-tongues|access-date=22 March 2018}}</ref><ref name="Babel">{{cite book|last1=Gordin|first1=Michael D.|title=Scientific Babel: How Science Was Done Before and After Global English|date=2015|publisher=University of Chicago Press|location=Chicago|isbn=978-0226000299}}</ref> Mendeleev has the distinction of accurately predicting the properties of what he called [[Dmitri Mendeleev's predicted elements|ekasilicon, ekaaluminium and ekaboron]] ([[germanium]], [[gallium]] and [[scandium]], respectively).<ref name="Marshall">{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Periodic Table  |journal=The Hexagon |date=2007 |pages=23–29 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/periodic%20table.pdf |access-date=30 December 2019}}</ref><ref name="Weeks">{{cite book |last1=Weeks |first1=Mary Elvira |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |location=Easton, PA |url=https://archive.org/details/discoveryoftheel002045mbp |edition=6th }}</ref>

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 (close to the modern value of 238).<ref>{{cite book |last1=Scerri |first1=Eric |author-link=Eric Scerri |title=The Periodic Table: Its Story and Its Significance |date=2019 |publisher=Oxford University Press |isbn=978-0190914363 |pages=142–143 |edition=2nd |url=https://books.google.com/books?id=tSa3DwAAQBAJ&q=mendeleev+uranium+120&pg=PA142 |access-date=13 December 2019}}</ref>

For his predicted three elements, he used the prefixes of eka, dvi, and tri ([[Sanskrit]] one, two, three) in their naming. Mendeleev questioned some of the currently accepted atomic weights (they could be measured only with a relatively low accuracy at that time), 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 [[lanthanide]]s, and predicted the existence of another row to the table which were the [[actinide]]s 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 ([[gallium]]) and Ge ([[germanium]]) were found in 1875 and 1886 respectively, fitting perfectly into the two missing spaces.<ref>{{cite book | last = Emsley | first = John | title = Nature's Building Blocks | publisher = Oxford University Press | year = 2001 | pages = [https://archive.org/details/naturesbuildingb0000emsl/page/521 521–522] | isbn = 978-0198503408 | url = https://archive.org/details/naturesbuildingb0000emsl/page/521 }}</ref>

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 (exemplified by the [[Shiva Sutras|Śivasūtras]] in [[Pāṇini]]'s [[Sanskrit grammar]]). Mendeleev was a friend and colleague of the Sanskritist [[Otto von Böhtlingk]], who was preparing the second edition of his book on [[Pāṇini]]<ref>Otto Böhtlingk, Panini's Grammatik: Herausgegeben, Ubersetzt, Erlautert und MIT Verschiedenen Indices Versehe. St. Petersburg, 1839–40.</ref> at about this time, and Mendeleev wished to honor [[Pāṇini]] with his nomenclature.<ref>Kiparsky, Paul. "Economy and the construction of the Sivasutras". In M.M. Deshpande and S. Bhate (eds.), ''Paninian Studies''. Ann Arbor, Michigan, 1991.</ref><ref>{{Cite journal| title=Mendeleev and the Periodic Table of Elements | first=Subhash | last=Kak | journal=Sandhan | volume = 4 | issue = 2 | pages=115–123 | year=2004 |arxiv=physics/0411080 | bibcode=2004physics..11080K}}</ref><ref>{{Cite web|url=https://www.americanscientist.org/article/the-grammar-of-the-elements|title=The Grammar of the Elements|date=4 October 2019|website=American Scientist|language=en|access-date=19 October 2019}}</ref>

The original draft made by Mendeleev would be found years later and published under the name ''Tentative System of Elements.''<ref>"[http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=33706 The Soviet Review Translations] {{Webarchive|url=https://web.archive.org/web/20140418233759/http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=33706 |date=18 April 2014 }}". Summer 1967. Vol. VIII, No. 2, M.E. Sharpe, Incorporated, p. 39</ref>

Dmitri Mendeleev is often referred to as the Father of the Periodic Table. He called his table or matrix, "the Periodic System".<ref>{{cite web|title=Dmitri Mendeleev|url=http://www.rsc.org/education/teachers/resources/periodictable/pre16/develop/mendeleev.htm|url-status=dead|archive-url=https://web.archive.org/web/20180705003658/http://www.rsc.org/education/teachers/resources/periodictable/pre16/develop/mendeleev.htm|archive-date=5 July 2018|access-date=23 February 2021|website=RSC Education|language=en}}</ref>