A chemistry course in schools begins in the 8th grade with a study of the general principles of science: possible types of bonds between atoms, types of crystal lattices and the most common reaction mechanisms are described. This becomes the foundation for the study of an important, but more specific section - inorganics.
What it is
Inorganic chemistry is a science that considers the principles of structure, basic properties and reactivity of all elements of the periodic table. An important role in the inorganic is played by the Periodic Law, which orders the systematic classification of substances by changing their mass, number and type.
The course also covers compounds formed by the interaction of table elements (the only exception is the hydrocarbon region, which is considered in the chapters of organics). Inorganic chemistry problems make it possible to work out the theoretical knowledge gained in practice.
Science in historical terms
The name "inorganic" appeared in accordance with the idea that it covers a part of chemical knowledge that is not related to the activity of biological organisms.
Over time, it was proved that most of the organic world can produce non-living compounds, and hydrocarbons of any type are synthesized in a laboratory. So, from the ammonium cyanate, which is a salt in element chemistry, the German scientist Wöhler was able to synthesize urea.
To avoid confusion with the nomenclature and classification of research types of both sciences, the program of school and university courses, following the general chemistry, involves the study of inorganics as a fundamental discipline. The scientific world maintains a similar sequence.
Classes of inorganic substances
Chemistry provides such a supply of material in which the introductory chapters of the inorganic consider the periodic law of the elements. This is a classification of a special type, which is based on the assumption that the atomic charges of nuclei affect the properties of substances, and these parameters change cyclically. Initially, the table was built as a reflection of the increase in atomic masses of elements, but soon this sequence was rejected due to its insolvency in the aspect in which inorganic substances require consideration of this issue.
Chemistry, in addition to the periodic table, suggests the presence of about a hundred figures, clusters and diagrams that reflect the periodicity of properties.
Currently, a consolidated version of the consideration of such a concept as inorganic chemistry classes is popular. The columns of the table indicate the elements depending on the physicochemical properties, the rows indicate periods similar to each other.
Simple substances in the inorganic
A sign in the periodic table and a simple substance in a free state are most often different things. In the first case, only the specific type of atoms is reflected, in the second, the type of compound of the particles and their mutual influence in stable forms.
The chemical bond in simple substances determines their division into families. Thus, two broad varieties of atomic groups can be distinguished — metals and non-metals. The first family has 96 elements out of 118 studied.
Metals
The metal type suggests the presence of the same bond between particles. The interaction is based on the socialization of the electrons of the lattice, which is characterized by non-directivity and unsaturation. That is why metals conduct heat well, charges, have a metallic luster, ductility and ductility.
Conventionally, metals are on the left in the periodic table when drawing a straight line from boron to astatine. Elements that are close in location to this line are most often borderline in nature and exhibit duality of properties (for example, germanium).
Most metals form the main compounds. The oxidation states of such substances usually do not exceed two. In the group, metallicity increases, and in the period decreases. For example, radioactive France exhibits more basic properties than sodium, and in the halogen family, iodine even appears metallic luster.
The situation is different in the period - inert gases complete the sublevels , in front of which there are substances with opposite properties. In the horizontal space of the periodic table, the manifested reactivity of the elements changes from basic through amphoteric to acidic. Metals are good reducing agents (accept electrons in the formation of bonds).
Non-metals
This type of atom is included in the main classes of inorganic chemistry. Non-metals occupy the right side of the periodic table, displaying typically acidic properties. Most often, these elements are found in the form of compounds with each other (for example, borates, sulfates, water). In a free molecular state, the existence of sulfur, oxygen and nitrogen is known. There are also several diatomic non-metal gases - in addition to the two mentioned above, they include hydrogen, fluorine, bromine, chlorine and iodine.
They are the most common substances on earth - silicon, hydrogen, oxygen and carbon are especially common. Iodine, selenium, and arsenic are very rare (this also includes the radioactive and unstable configurations that are located in the last periods of the table).
In compounds, non-metals behave predominantly as acids. They are powerful oxidizing agents due to the possibility of adding an additional number of electrons to complete the level.
Complex substances in the inorganic
In addition to substances that are represented by one group of atoms, there are compounds that include several different configurations. Such substances can be binary (consisting of two different particles), three-, four-element, and so on.
Two-element substances
Chemistry attaches particular importance to the binding binary in molecules. Classes of inorganic compounds are also considered from the point of view of the bond formed between the atoms. It can be ionic, metallic, covalent (polar or non-polar) or mixed. Typically, such substances clearly show the basic (in the presence of metal), amphora (dual - especially characteristic of aluminum) or acidic (if there is an element with an oxidation state of +4 or higher) qualities.
Three element associates
Inorganic chemistry topics include consideration of this type of association of atoms. Compounds consisting of more than two groups of atoms (most often inorganics deal with three-element species) are usually formed with the participation of components that differ significantly in physicochemical parameters.
Possible types of bonds are covalent, ionic and mixed. Usually, three-element substances are similar in behavior to binary due to the fact that one of the forces of interatomic interaction is much stronger than the other: a weak one is formed in the second place and has the ability to dissociate in solution faster.
Inorganic chemistry classes
The vast majority of substances studied in the course of inorganics can be considered by a simple classification depending on their composition and properties. So, there are hydroxides, acids, oxides and salts. Consideration of their relationship is best to begin with an introduction to the concept of oxidized forms, which can be almost any inorganic substance. The chemistry of such associates is discussed in chapters on oxides.
Oxides
An oxide is a compound of any chemical element with oxygen in an oxidation state equal to -2 (in peroxides -1, respectively). The bond is formed due to the recoil and addition of electrons with the reduction of O 2 (when oxygen is the most electronegative element).
They may exhibit acidic, amphoteric, and basic properties depending on the second group of atoms. If it is a metal, in the oxide it does not exceed the oxidation state +2, if non-metal - from +4 and above. In samples with a dual nature of parameters, a value of +3 is achieved.
Acids in the inorganic
Acid compounds have a reaction of a medium of less than 7 due to the content of hydrogen cations, which can go into solution and subsequently be replaced by a metal ion. According to the classification are complex substances. Most acids can be obtained by diluting the corresponding oxides with water, for example, during the formation of sulfuric acid after hydration with SO 3 .
Basic inorganic chemistry
The properties of this type of compounds are due to the presence of OH hydroxyl radical, which gives a reaction of a medium higher than 7. Soluble bases are called alkalis, they are the strongest in this class of substances due to complete dissociation (decomposition into ions in a liquid). The OH group during salt formation can be replaced by acid residues.
Inorganic chemistry is a dual science that can describe substances from different points of view. In the protolytic theory, bases are considered as acceptors of a hydrogen cation. This approach broadens the concept of this class of substances, calling alkali any substance capable of accepting a proton.
Salt
This type of compound is between bases and acids, as it is a product of their interaction. So, usually a metal ion acts as a cation (sometimes ammonium, phosphonium or hydroxonium), and an acid residue as an anionic substance. When salt is formed, hydrogen is replaced by another substance.
Depending on the ratio of the number of reagents and their strength in relation to each other, it is rational to consider several types of interaction products:
- basic salts are obtained if the hydroxyl groups are not completely substituted (such substances have an alkaline reaction of the medium);
- acid salts are formed in the opposite case - with a lack of a reacting base, hydrogen partially remains in the compound;
- the most famous and simplest to understand are medium (or normal) samples - they are the product of the complete neutralization of reagents with the formation of water and a substance only with a metal cation or its analogue and an acid residue.
Inorganic chemistry is a science that involves dividing each of the classes into fragments that are considered at different times: some earlier, others later. With a more in-depth study, 4 more types of salts are distinguished:
- Doubles contain a single anion in the presence of two cations. Typically, such substances are obtained by merging two salts with the same acid residue, but different metals.
- The mixed type is the opposite of the previous one: its basis is one cation with two different anions.
- Crystal hydrates are salts in the formula of which there is water in a crystallized state.
- Complexes are substances in which a cation, anion, or both of them are presented in the form of clusters with a forming element. Such salts can be obtained predominantly from elements of subgroup B.
Other substances included in the inorganic chemistry workshop that can be classified as salts or as separate chapters of knowledge include hydrides, nitrides, carbides, and intermetallics (compounds of several metals that are not an alloy).
Summary
Inorganic chemistry is a science that is of interest to every specialist in this field, regardless of his interests. It includes the first chapters studied at school in this subject. The course of inorganic chemistry provides for the systematization of large amounts of information in accordance with a clear and simple classification.