Dmitri Ivanovich Mendeleev, in Russian Дмитрий Иванович Менделеев, (8 February 1834-2 February 1907) was a Russian chemist and inventor.
He is best known for formulating the Periodic Law and creating a farsighted 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.
Mendeleev was born in the village of Verkhnie Aremzyani, near Tobolsk in Siberia, to Ivan Pavlovich Mendeleev (1783-1847) and Maria Dmitrievna Mendeleeva (née Kornilieva) (1793–1850).
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.
Mendeleev's 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, in Russian Основы химии, 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.
By adding additional elements following this pattern, Mendeleev developed his extended version of the periodic table.
More information: BBC
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. 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 (Pt, Ir, Os) or have their atomic weights increasing regularly (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 has the distinction of accurately predicting the properties of what he called ekasilicon, ekaaluminium and ekaboron (germanium, gallium and scandium, respectively).
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.
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 lanthanides, and predicted the existence of another row to the table which were the actinides which were some of the heaviest in atomic weight.
More information: Origins
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.
By using Sanskrit prefixes to name missing elements, Mendeleev may have recorded his debt to the Sanskrit grammarians of ancient India, who had created sophisticated theories of language based on their discovery of the two-dimensional patterns of speech sounds, arguably most strikingly exemplified by the 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 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.
In 1905, Mendeleev was elected a member of the Royal Swedish Academy of Sciences. The following year the Nobel Committee for Chemistry recommended to the Swedish Academy to award the Nobel Prize in Chemistry for 1906 to Mendeleev for his discovery of the periodic system.
In 1907, Mendeleev died at the age of 72 in Saint Petersburg from influenza.
More information: Elsevier
exhibit an apparent periodicity of properties.
Dmitri Mendeleev
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