Fundamentals of inorganic chemistry. Degree of oxidation

The degree of oxidation is a conditional charge of an atomelement in the molecule. This concept is fundamental in inorganic chemistry, without its understanding it is impossible to imagine the processes of oxidation-reduction reactions, the types of bonds in molecules, the 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, neutronsand 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. Consequently, the atom is neutral.

Each electron has a certain levelenergy, which determines the proximity of its location to the core: the closer to the core - 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 at the external energy level are not too strongly associated with the nucleus, so they can participate in chemical reactions. Elements that have at the outer level of one to four electrons in the chemical reactions, as a rule, give off electrons, and those that have five to seven electrons - accept.

There are also chemical elements calledinert 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 greaterelectronegativity "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 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⁺²ABOUT^-2.

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

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