![]() ![]() ![]() The Periodic Law’s discovery was one of the most momentous events in the history of chemical science. The periodic recurrence of elements with comparable physical and chemical properties derives directly from the periodic recurrence of identical electronic configurations in respective atoms’ outer shells when elements are enumerated in increasing atomic number order. The Periodic Law had no scientific explanation at first, and it was solely utilized as an empirical principle but, with the development of quantum physics, the theoretical basis for the Periodic Law could be understood. Lothar Meyer’s table was presented several months after Mendeleev’s, but he disagreed with Mendeleev’s Periodic law. In 1913, Henry Moseley found that the atomic number, not the atomic weight, determines periodicity. Mendeleev also proposed an elemental periodic system based on the chemical and physical properties of the elements and their compounds, rather than only atomic weights. After a number of nineteenth-century scientific investigations, Russian chemist Dmitri Mendeleev discovered this principle in 1871. Many of the physical and chemical properties of lithium, such as its vigorous reactivity with water, recur in sodium, potassium, and cesium after arranging elements in increasing atomic numbers. The Periodic Law asserts that when chemical elements are enumerated in increasing atomic number order, many of their properties undergo cyclical changes, with comparable elements reoccurring at regular intervals. According to this criterion, pyridine is more aromatic than furan, but it is difficult to say by how much. As a result, the degree of aromaticity is measured in terms of reactivity by the relative tendency toward substitution rather than addition. The extra stability, in turn, determines the compound’s tendency to react by substitution of hydrogen-that is, replacement of a singly bonded hydrogen atom with another singly bonded atom or group-rather than the addition of one or more atoms to the molecule via the breaking of a double bond (see substitution reaction addition reaction). ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |