[WORLDKINGS] On this day - March 6, 2023 – 154th anniversary of the first periodic table of chemical elements presented by Dmitri Mendeleev (1869)

06-03-2023

(Worldkings.org) Other scientists had previously identified periodicity of elements, but on March 6, 1869 Dmitri Mendeleev presented the first periodic table.

Mendeleev was a Russian chemist and professor, who wrote chemistry textbooks to meet his needs. While composing a book for inorganic chemistry, he attempted to classify the elements according to their chemical properties, and noticed patterns that led him to postulate his periodic table. His table appeared in his textbook The Principles of Chemistry in 1869.

A handful of other scientists had been working on similar projects in the 1860s, but history records Mendeleev as being unaware of such work.

 

On March 6, 1869, he 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.

Mendeleev then published his periodic table of all known elements in a Russian journal and predicted several new elements to complete the table. Below you can see the table as it appeared in 1869 in the German journal, Zeitschrift für Chemie, where Mendeleev stated:

  1. The elements, if arranged according to their atomic mass, exhibit an apparent periodicity of properties.
  2. Elements which are similar as 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, or of groups of elements in the order of their atomic masses, 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, elements analogous to aluminium and silicon – whose atomic weight 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.
  8. Certain characteristic properties of elements can be foretold from their atomic masses.

 

Only a few months later, German chemist Julius Lothar Meyer published a virtually identical table. Mendeleev and Meyer are often both credited with the table, but for his predicted eight elements, Mendeleev often received the majority of the credit. He used the prefixes of eka, dvi, and tri (Sanskrit one, two, three) in their naming.

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 his table and predictions.

 

According to edn.com


Kyna ( Collect) - WORLDKINGS (Source of photos: Internet)

 

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