Difference between classical and modern formulation of Mendeleev's periodic law.

The famous Russian scientist Dmitry Ivanovich Mendeleev formulated the periodic law back in the 19th century, which had an exceptionally great influence on the development of physics, chemistry and science in general. But since then, the corresponding concept has undergone a number of changes. What are they?

Mendeleev's periodic law: the original formulation

In 1871, D. I. bodies formed by them (simple and complex) should be considered as being in periodic dependence on the indices of their atomic weight.

This formulation was published in the author's article by DI Mendeleev "Periodic validity of chemical elements". The corresponding publication was preceded by a great work of the scientist in the field of research of physical and chemical processes. In 1869, news appeared in the Russian scientific community about the discovery by DI Mendeleev of the Periodic Law of Chemical Elements. Soon a textbook was published, in which one of the first versions of the famous periodic table was published.

DI Mendeleev first introduced the term "periodic law" to the general public in 1870, in one of his scientific articles. In this material, the scientist pointed out the fact that there are not yet discovered chemical elements. Mendeleev justified this by the fact that the properties of each individual chemical element are intermediate between the characteristics of those that are adjacent to it on the periodic table. Moreover, both in the group and in the period. That is, the properties of an element are intermediate between the characteristics of elements located above and below the table relative to it, as well as those located to the right and left.

The periodic table has become a unique result of scientific works. In addition, the fundamental novelty of Mendeleev's concept was that, firstly, he explained the regularities in the ratios of the atomic masses of chemical elements, and secondly, he invited the community of researchers to consider these regularities as a law of nature.

Within several years after the publication of Mendeleev's periodic law, chemical elements that were not known at the time of publication of the corresponding concept, but predicted by scientists, were discovered. Gallium was discovered in 1875. In 1879 - scandium, in 1886 - germanium. Mendeleev's periodic law has become the undeniable theoretical basis of chemistry.

The modern formulation of the periodic law

With the development of chemistry and physics, the concept of DI Mendeleev developed. So, in the late 19th - early 20th centuries, scientists were able to explain the physical meaning of a particular atomic number of a chemical element. Later, the researchers developed a model of changes in the electronic structure of atoms in correlation with the growth of charges of the nuclei of the corresponding atoms.

Now the formulation of the periodic law - taking into account the above and other discoveries of scientists - is somewhat different from the one proposed by DI Mendeleev. In accordance with it, the properties of the elements, as well as the substances formed by them (as well as their forms) are characterized by a periodic dependence on the charges of the nuclei of the atoms of the corresponding elements.

Comparison

The main difference between the classical formulation of the periodic Mendeleev's law and the modern one is that the initial interpretation of the corresponding scientific law presupposes the dependence of the properties of elements and the compounds formed by them on indicators of their atomic weight. The modern interpretation also assumes the presence of a similar dependence - but predetermined by the charge of the nuclei of atoms of chemical elements. One way or another, scientists came to the second formulation, over time developing the first through painstaking work.

Having determined what is the difference between the classical and modern formulations of the periodic law of Mendeleev, we will reflect the conclusions in the table.

Table

Formulation of the periodic law of Mendeleev Modern formulation of the periodic law
What do they have in common?
Both concepts imply a periodic dependence of the properties of elements and the compounds formed by them on certain factors
What is the difference between them?
DI Mendeleev proposed a formulation according to which the properties of elements have a periodic dependence on their atomic weightwhich properties of elements have a periodic dependence on the charge of the nuclei of their atoms
.