mendeleev

Dmitri Ivanovich Mendeleev (also romanized Mendeleyev or Mendeleef was a Russian chemist and inventor. He
is credited as being the creator of the first version of the periodic table of elements. Using the table, he predicted the properties of elements yet to be discovered.
Others had suggested that the elements display periodicity. One was John Newlands, who published his Law of Octaves in 1865. The lack of spaces for undiscovered elements and the placing of two elements in one box were criticized and his ideas were not accepted. Another was Lothar Meyer, who published a work in 1864, describing 28 elements. Neither attempted to predict new elements. In 1863 there were 56 known elements with a new element being discovered at a rate of approximately one per year.
After becoming a teacher, Mendeleev wrote the definitive two-volume textbook at that time: Principles of Chemistry (1868-1870). As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his Periodic Table. Mendeleev was unaware of the other work on periodic tables going on in the 1860s. He made the following table, and by adding additional elements following this pattern, developed his extended version of the periodic table.
Cl 35.5 K 39 Ca 40
Br 80 Rb 85 Sr 88
I 127 Cs 133 Ba 137
On 6 March 1869, Mendeleev made a formal presentation to the Russian Chemical Society, entitled 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
1. The elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties.
2. Elements which are similar in regards to their chemical properties have atomic weights which are either of nearly the same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs).
3. 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.
4. The elements which are the most widely diffused have small atomic weights.
5. 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.
6. 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.
7. 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. Here Mendeleev was wrong as the atomic mass of tellurium (127.6) remains higher than that of iodine (126.9).
8. 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. Only a few months after, Meyer published a virtually identical table. Some consider Meyer and Mendeleev the co-creators of the periodic table, but virtually everybody agrees that Mendeleev's accurate prediction of the qualities of what he called ekasilicon, ekaaluminium and ekaboron (germanium, gallium and scandium, respectively) qualifies him for the majority of the credit for the table.
For his predicted eight 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 mass. 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 giving Sanskrit names to his "missing" elements, Mendeleev showed his appreciation and debt to the Sanskrit grammarians of ancient India, who had created sophisticated theories of language based on their discovery of the two-dimensional patterns in basic sounds. According to Professor Paul Kiparsky of Stanford University, Mendeleev was a friend and colleague of the Sanskritist Böhtlingk, who was preparing the second edition of his book on Pānini at about this time, and Mendeleev wished to honor Pānini with his nomenclature. Noting that there are striking similarities between the Periodic Table and the introductory Śiva Sūtras in Panini’s grammar, Prof. Kiparsky says:
[T]he analogies between the two systems are striking. Just as Panini found that the phonological patterning of sounds in the language is a function of their articulatory properties, so Mendeleev found that the chemical properties of elements are a function of their atomic weights. Like Panini, Mendeleev arrived at his discovery through a search for the "grammar" of the elements...