At the moment, more than five hundred thousand inorganic compounds have been identified. The classification and nomenclature of inorganic substances is an important issue that allows one to understand the variety of compounds.
History reference
In the XVIII – XIX centuries, Antoine Lavoisier, Mikhail Lomonosov, John Dalton proposed the first classification and nomenclature of inorganic substances. Simple and complex substances stood out . The first group was divided into metals and non-metals. A group of compounds that had intermediate properties called metalloids was also isolated. This division formed the basis of modern classification.
There are currently four classes. Let's take a closer look at each of these classes.
Oxides
They are polyatomic compounds, which consist of two elements, the second in them is always an oxygen ion in oxidation state -2. The classification and nomenclature of inorganic substances involves the division of the class of oxides into three groups:
Classification
The first group consists of metal compounds (with minimal oxidation state) with oxygen. For example, MgO is magnesium oxide. Among the main chemical properties of this compound, their interaction with acid oxides, acids, and more active metals can be noted.
Acid oxides include oxygen compounds of non-metals, as well as metal elements with oxidation states from +4 to +7. For example, this group includes MnO 2 , CO 2 . Among the typical chemical properties of carbon dioxide, we single out the interaction with water (a weak carbonic acid is formed), basic oxides, and soluble bases (alkalis).
Amphoteric (transitional) oxides are metal compounds with an oxidation state of +3 (as well as beryllium oxide, zinc), which are capable of interacting with both acids and alkalis.
Oxides are divided into salt-forming and non-salt-forming. The first group corresponds to acids or bases in which the oxidation state is retained in the main element. The non-salt-forming group is small, its representatives are not able to form salts. For example, among non-salt-forming oxides, N 2 O, NO, SiO, CO.
Hydroxides
The classification and nomenclature of inorganic substances involves the allocation of a class of hydroxides. They are called complex substances, in the composition of which there are atoms of some element, as well as OH hydroxyl groups. This class is divided into two large groups:
Acids contain several hydrogen atoms that can be replaced by metal atoms subject to the rules of stoichiometric valency. Many acid hydroxides (acids) are in meta-form, and the hydrogen atoms in them are located at the beginning of the formula. They have a general view of HxEOy, where the second part is called the acid residue. The classification of inorganic substances and their nomenclature is considered as part of the school chemistry course. For example, salts of sulfuric acid - sulfates, nitric acid - nitrates, carbonic acid - carbonates.
Depending on the number of hydrogen atoms, the following groups are distinguished:
- monobasic;
- dibasic;
- tribasic acids
According to the oxygen content, acids are divided into oxygen-containing and not containing compounds.
The bases in their composition contain metal and OH cations, which are capable of being replaced by acid residues in chemical reactions, subject to the rules of stoichiometric valency.
The bases are in the ortho form, have the general formula M (OH) n, with n = 1 or 2. When the compounds of this group are named, the corresponding metal is added to the hydroxide.
Among the basic chemical properties possessed by representatives of this box office of inorganic substances, it is necessary to note their reaction with acids, the reaction products are water and salt.
For example, in the reaction of sodium hydroxide with hydrochloric acid, the products are water and sodium chloride.
Depending on the solubility in water, soluble bases (alkalis) and insoluble hydroxides are isolated. The first group includes hydroxyl compounds of metals of the first and second groups of the main subgroups (alkaline and alkaline earth metals).
For example, NaOH - alkali (sodium hydroxide); Fe (OH) 2 - iron hydroxide II (insoluble compound).
Salt
What else includes the classification and nomenclature of inorganic substances? Tasks for students in grades 8–9 involve dividing the proposed list of compounds into separate classes: oxides, bases, acids, salts.
Salts are complex substances in which metal cations and anions of the acid residue are present. Middle salts have the general formula Mx (EOy) n . An example of this group is Ca 3 (PO 4 ) 2 - calcium phosphate.
If hydrogen cations also appear in the composition, the salts are called acidic, and the presence of hydroxyl groups is characteristic of the basic salts. For example, NaHCO 3 is sodium bicarbonate, and CaOHCl is calcium hydroxyl chloride.
Those salts, in the composition of which cations of two different metals are present, they are called double.
Complex salts are complex compounds that contain a complexing agent and ligands. In high school, the classification and nomenclature of inorganic substances is considered. The theory of complex compounds is being studied as part of a core course in general chemistry. Questions regarding the nomenclature and chemical properties of complex salts are not included in the test questions of the unified state chemistry exam for a high school course.
Conclusion
How is the classification and nomenclature of inorganic substances used in the school curriculum? Briefly, groups of substances are considered in the framework of the eighth and ninth grade programs, and they are studied in more detail in the course of general chemistry of 11th grade. Tasks relating to the classification of inorganic compounds, comparing the chemical properties of the compounds with the products offered, are included in the final certification tests in chemistry (USE) for graduates of the eleventh grade. In order to successfully cope with them, students must have basic knowledge on the classification of inorganic compounds, the skills to compare the proposed substances with the chemical properties of the entire class.