Fundamentals of inorganic chemistry. Degree of oxidation

The degree of oxidation is the conditioned charge of the atom of the element in the molecule. This concept is fundamental in inorganic chemistry, without its understanding it is impossible to imagine the processes of oxidation-reduction reactions, types of bonds in molecules, chemical and physical properties of elements. In order to understand what is the degree of oxidation, you first need to understand what the atom consists of and how it behaves when interacting with oneself like.

As is known, the atom consists of protons, neutrons and electrons. Protons and electrons, also called nucleons, form a positively charged nucleus around which negative electrons rotate around it. The positive charge of the nucleus is balanced by the total negative charge of the electrons. Therefore, the atom is neutral.

Each electron has a certain level of energy, which determines the proximity of its location to the nucleus: the closer to the nucleus - the less energy. They are arranged in layers. Electrons of one layer have practically the same energy reserve and form an energy level or an electronic layer. Electrons on the external energy level are not too strongly associated with the nucleus, so they can participate in chemical reactions. Elements that have on the outer level of one to four electrons, in the chemical reactions, as a rule, give electrons, and those that have five to seven electrons - accept.

There are also chemical elements called inert gases, in which the external energy level contains eight electrons - the maximum possible number. They practically do not enter into chemical reactions. So, any atom tends to "supplement" its external electronic layer to the required eight electrons. Where to get the missing? For other atoms. In the process of chemical reaction, the element with greater electronegativity "takes" the electron from an element with a smaller electronegativity. The electronegativity of a chemical element depends on the number of electrons at the valence level and the force of their attraction to the core. In the element that takes away electrons, the total negative charge becomes larger than the positive charge of the nucleus, and for the electron that gives up, it is vice versa. For example, in a sulfur oxide compound SO, oxygen having greater electronegativity takes 2 electrons from the sulfur and acquires a negative charge, while sulfur, remaining without two electrons, receives a positive charge. In this case, the degree of oxidation of oxygen is equal to the degree of oxidation of sulfur taken with the opposite sign. The degree of oxidation is recorded in the upper right corner of the chemical element. In our example, it looks like this: S ⁺² O ^-2 .

The above example is rather simplistic. In fact, the outer electrons of one atom never completely shift to another, they only become "common", therefore, the oxidation states of elements are always less than those designated in textbooks.

But to simplify the understanding of chemical processes this fact is neglected.