Co2 in the solid state is made up of molecules. Atomic-molecular doctrine
The atomic-molecular theory was developed and first applied in chemistry by the great Russian scientist M.V. Lomonosov. The main provisions of this doctrine are set forth in the work "Elements of Mathematical Chemistry" (1741) and a number of others. The essence of Lomonosov's teachings can be reduced to the following provisions.
1. All substances consist of "corpuscles" (as Lomonosov called molecules).
2. Molecules consist of "elements" (as Lomonosov called atoms).
3. Particles - molecules and atoms - are in continuous motion. The thermal state of bodies is the result of the motion of their particles.
4. Molecules of simple substances consist of identical atoms, molecules of complex substances consist of different atoms.
67 years after Lomonosov, the English scientist John Dalton applied the atomistic doctrine in chemistry. He outlined the main provisions of atomism in the book "The New System of Chemical Philosophy" (1808). At its core, Dalton's teaching repeats the teachings of Lomonosov. However, Dalton denied the existence of molecules in simple substances, which, in comparison with the teachings of Lomonosov, is a step backwards. According to Dalton, simple substances consist only of atoms, and only complex substances - of "complex atoms" (in the modern sense - molecules). The atomic-molecular doctrine in chemistry was finally established only in the middle of the 19th century. At the international congress of chemists in Karlsruhe in 1860, definitions of the concepts of a molecule and an atom were adopted.
A molecule is the smallest particle of a given substance that has its chemical properties. The chemical properties of a molecule are determined by its composition and chemical structure.
An atom is the smallest particle of a chemical element that is part of the molecules of simple and complex substances. The chemical properties of an element are determined by the structure of its atom. From this follows the definition of the atom, corresponding to modern ideas:
An atom is an electrically neutral particle consisting of a positively charged atomic nucleus and negatively charged electrons.
According to modern ideas, substances in the gaseous and vaporous state are composed of molecules. In the solid state, molecules consist only of substances whose crystal lattice has a molecular structure. Most solid inorganic substances do not have a molecular structure: their lattice does not consist of molecules, but of other particles (ions, atoms); they exist in the form of macrobodies (a crystal of sodium chloride, a piece of copper, etc.). Salts, metal oxides, diamond, silicon, metals do not have a molecular structure.
Chemical elements
The atomic and molecular theory made it possible to explain the basic concepts and laws of chemistry. From the point of view of atomic and molecular science, each separate type of atom is called a chemical element. The most important characteristic of an atom is the positive charge of its nucleus, numerically equal to the ordinal number of the element. The value of the charge of the nucleus serves as a distinguishing feature for different types of atoms, which allows us to give a more complete definition of the concept of an element:
Chemical element A certain type of atom with the same positive nuclear charge.
107 elements are known. Currently, work continues on the artificial production of chemical elements with higher serial numbers.
All elements are usually divided into metals and non-metals. However, this division is conditional. An important characteristic of the elements is their abundance in the earth's crust, i.e. in the upper solid shell of the Earth, the thickness of which is conventionally assumed to be 16 km. The distribution of elements in the earth's crust is studied by geochemistry, the science of the chemistry of the earth. Geochemist A.P. Vinogradov compiled a table of the average chemical composition of the earth's crust. According to these data, the most common element is oxygen - 47.2% of the mass of the earth's crust, followed by silicon - 27.6, aluminum - 8.80, iron -5.10, calcium - 3.6, sodium - 2.64, potassium - 2.6, magnesium - 2.10, hydrogen - 0.15%.
Covalent chemical bond, its varieties and formation mechanisms. Characteristics of a covalent bond (polarity and bond energy). Ionic bond. Metal connection. hydrogen bond
The doctrine of the chemical bond is the basis of all theoretical chemistry.
A chemical bond is such an interaction of atoms that binds them into molecules, ions, radicals, crystals.
There are four types of chemical bonds: ionic, covalent, metallic and hydrogen.
The division of chemical bonds into types is conditional, since all of them are characterized by a certain unity.
An ionic bond can be considered as the limiting case of a covalent polar bond.
A metallic bond combines the covalent interaction of atoms with the help of shared electrons and the electrostatic attraction between these electrons and metal ions.
In substances, there are often no limiting cases of chemical bonding (or pure chemical bonds).
For example, lithium fluoride $LiF$ is classified as an ionic compound. In fact, the bond in it is $80%$ ionic and $20%$ covalent. Therefore, it is obviously more correct to speak of the degree of polarity (ionicity) of a chemical bond.
In the hydrogen halide series $HF—HCl—HBr—HI—HAt$, the degree of bond polarity decreases, because the difference in the electronegativity values of the halogen and hydrogen atoms decreases, and in astatic hydrogen the bond becomes almost nonpolar $(EO(H) = 2.1; EO(At) = 2.2)$.
Different types of bonds can be contained in the same substances, for example:
- in bases: between the oxygen and hydrogen atoms in the hydroxo groups, the bond is polar covalent, and between the metal and the hydroxo group is ionic;
- in salts of oxygen-containing acids: between the non-metal atom and the oxygen of the acid residue - covalent polar, and between the metal and the acid residue - ionic;
- in salts of ammonium, methylammonium, etc.: between nitrogen and hydrogen atoms - covalent polar, and between ammonium or methylammonium ions and an acid residue - ionic;
- in metal peroxides (for example, $Na_2O_2$) the bond between oxygen atoms is covalent non-polar, and between the metal and oxygen it is ionic, and so on.
Different types of connections can pass one into another:
- during electrolytic dissociation in water of covalent compounds, a covalent polar bond passes into an ionic one;
- during the evaporation of metals, the metallic bond turns into a covalent non-polar, etc.
The reason for the unity of all types and types of chemical bonds is their identical chemical nature - electron-nuclear interaction. The formation of a chemical bond in any case is the result of an electron-nuclear interaction of atoms, accompanied by the release of energy.
Methods for the formation of a covalent bond. Characteristics of a covalent bond: bond length and energy
A covalent chemical bond is a bond that occurs between atoms due to the formation of common electron pairs.
The mechanism of formation of such a bond can be exchange and donor-acceptor.
I. exchange mechanism acts when atoms form common electron pairs by combining unpaired electrons.
1) $H_2$ - hydrogen:
The bond arises due to the formation of a common electron pair by $s$-electrons of hydrogen atoms (overlapping $s$-orbitals):
2) $HCl$ - hydrogen chloride:
The bond arises due to the formation of a common electron pair of $s-$ and $p-$electrons (overlapping $s-p-$orbitals):
3) $Cl_2$: in a chlorine molecule, a covalent bond is formed due to unpaired $p-$electrons (overlapping $p-p-$orbitals):
4) $N_2$: three common electron pairs are formed between atoms in a nitrogen molecule:
II. Donor-acceptor mechanism Let us consider the formation of a covalent bond using the example of the ammonium ion $NH_4^+$.
The donor has an electron pair, the acceptor has an empty orbital that this pair can occupy. In the ammonium ion, all four bonds with hydrogen atoms are covalent: three were formed due to the creation of common electron pairs by the nitrogen atom and hydrogen atoms by the exchange mechanism, one - by the donor-acceptor mechanism.
Covalent bonds can be classified by the way in which the electron orbitals overlap, as well as by their displacement towards one of the bonded atoms.
Chemical bonds formed as a result of the overlap of electron orbitals along the bond line are called $σ$ -bonds (sigma-bonds). The sigma bond is very strong.
$p-$orbitals can overlap in two regions, forming a covalent bond through lateral overlap:
Chemical bonds formed as a result of the "lateral" overlapping of electron orbitals outside the communication line, i.e. in two regions are called $π$ -bonds (pi-bonds).
By degree of bias common electron pairs to one of the atoms they bond, a covalent bond can be polar and non-polar.
A covalent chemical bond formed between atoms with the same electronegativity is called non-polar. Electron pairs are not shifted to any of the atoms, because atoms have the same ER - the property of pulling valence electrons towards themselves from other atoms. For example:
those. through a covalent non-polar bond, molecules of simple non-metal substances are formed. A covalent chemical bond between atoms of elements whose electronegativity differs is called polar.
The length and energy of a covalent bond.
characteristic covalent bond properties is its length and energy. Link length is the distance between the nuclei of atoms. A chemical bond is stronger the shorter its length. However, the measure of bond strength is binding energy, which is determined by the amount of energy required to break the bond. It is usually measured in kJ/mol. Thus, according to experimental data, the bond lengths of $H_2, Cl_2$, and $N_2$ molecules are $0.074, 0.198$, and $0.109$ nm, respectively, and the binding energies are $436, 242$, and $946$ kJ/mol, respectively.
Ions. Ionic bond
Imagine that two atoms "meet": a metal atom of group I and a non-metal atom of group VII. A metal atom has a single electron in its outer energy level, while a non-metal atom lacks just one electron to complete its outer level.
The first atom will easily give up to the second its electron, which is far from the nucleus and weakly bound to it, and the second will give it a free place on its outer electronic level.
Then an atom, deprived of one of its negative charges, will become a positively charged particle, and the second will turn into a negatively charged particle due to the received electron. Such particles are called ions.
The chemical bond that occurs between ions is called ionic.
Consider the formation of this bond using the well-known sodium chloride compound (table salt) as an example:
The process of transformation of atoms into ions is shown in the diagram:
Such a transformation of atoms into ions always occurs during the interaction of atoms of typical metals and typical non-metals.
Consider the algorithm (sequence) of reasoning when recording the formation of an ionic bond, for example, between calcium and chlorine atoms:
Numbers showing the number of atoms or molecules are called coefficients, and the numbers showing the number of atoms or ions in a molecule are called indexes.
metal connection
Let's get acquainted with how the atoms of metal elements interact with each other. Metals do not usually exist in the form of isolated atoms, but in the form of a piece, ingot, or metal product. What holds metal atoms together?
The atoms of most metals at the outer level contain a small number of electrons - $1, 2, 3$. These electrons are easily detached, and the atoms are converted into positive ions. The detached electrons move from one ion to another, binding them into a single whole. Connecting with ions, these electrons temporarily form atoms, then break off again and combine with another ion, and so on. Consequently, in the volume of a metal, atoms are continuously converted into ions and vice versa.
The bond in metals between ions by means of socialized electrons is called metallic.
The figure schematically shows the structure of a sodium metal fragment.
In this case, a small number of socialized electrons binds a large number of ions and atoms.
The metallic bond bears some resemblance to the covalent bond, since it is based on the sharing of outer electrons. However, in a covalent bond, the outer unpaired electrons of only two neighboring atoms are socialized, while in a metallic bond, all atoms take part in the socialization of these electrons. That is why crystals with a covalent bond are brittle, while those with a metal bond are, as a rule, plastic, electrically conductive, and have a metallic sheen.
The metallic bond is characteristic of both pure metals and mixtures of various metals - alloys that are in solid and liquid states.
hydrogen bond
A chemical bond between positively polarized hydrogen atoms of one molecule (or part of it) and negatively polarized atoms of strongly electronegative elements having unshared electron pairs ($F, O, N$ and less often $S$ and $Cl$), another molecule (or its parts) is called hydrogen.
The mechanism of hydrogen bond formation is partly electrostatic, partly donor-acceptor.
Examples of intermolecular hydrogen bonding:
In the presence of such a bond, even low molecular weight substances can under normal conditions be liquids (alcohol, water) or easily liquefying gases (ammonia, hydrogen fluoride).
Substances with a hydrogen bond have molecular crystal lattices.
Substances of molecular and non-molecular structure. Type of crystal lattice. The dependence of the properties of substances on their composition and structure
Molecular and non-molecular structure of substances
It is not individual atoms or molecules that enter into chemical interactions, but substances. A substance under given conditions can be in one of three states of aggregation: solid, liquid or gaseous. The properties of a substance also depend on the nature of the chemical bond between the particles that form it - molecules, atoms or ions. According to the type of bond, substances of molecular and non-molecular structure are distinguished.
Substances made up of molecules are called molecular substances. The bonds between molecules in such substances are very weak, much weaker than between atoms inside a molecule, and already at relatively low temperatures they break - the substance turns into a liquid and then into a gas (iodine sublimation). The melting and boiling points of substances consisting of molecules increase with increasing molecular weight.
Molecular substances include substances with an atomic structure ($C, Si, Li, Na, K, Cu, Fe, W$), among them there are metals and non-metals.
Consider the physical properties of alkali metals. The relatively low bond strength between atoms causes low mechanical strength: alkali metals are soft and can be easily cut with a knife.
The large sizes of atoms lead to a low density of alkali metals: lithium, sodium and potassium are even lighter than water. In the group of alkali metals, the boiling and melting points decrease with an increase in the ordinal number of the element, because. the size of the atoms increases and the bonds weaken.
To substances non-molecular structures include ionic compounds. Most compounds of metals with non-metals have this structure: all salts ($NaCl, K_2SO_4$), some hydrides ($LiH$) and oxides ($CaO, MgO, FeO$), bases ($NaOH, KOH$). Ionic (non-molecular) substances have high melting and boiling points.
Crystal lattices
A substance, as is known, can exist in three states of aggregation: gaseous, liquid and solid.
Solids: amorphous and crystalline.
Consider how the features of chemical bonds affect the properties of solids. Solids are divided into crystalline and amorphous.
Amorphous substances do not have a clear melting point - when heated, they gradually soften and become fluid. In the amorphous state, for example, are plasticine and various resins.
Crystalline substances are characterized by the correct arrangement of the particles of which they are composed: atoms, molecules and ions - at strictly defined points in space. When these points are connected by straight lines, a spatial frame is formed, called the crystal lattice. The points at which crystal particles are located are called lattice nodes.
Depending on the type of particles located at the nodes of the crystal lattice, and the nature of the connection between them, four types of crystal lattices are distinguished: ionic, atomic, molecular and metal.
Ionic crystal lattices.
Ionic called crystal lattices, in the nodes of which there are ions. They are formed by substances with an ionic bond, which can bind both simple ions $Na^(+), Cl^(-)$, and complex $SO_4^(2−), OH^-$. Consequently, salts, some oxides and hydroxides of metals have ionic crystal lattices. For example, a sodium chloride crystal consists of alternating $Na^+$ positive ions and $Cl^-$ negative ions, forming a cube-shaped lattice. The bonds between ions in such a crystal are very stable. Therefore, substances with an ionic lattice are characterized by relatively high hardness and strength, they are refractory and non-volatile.
Atomic crystal lattices.
nuclear called crystal lattices, in the nodes of which there are individual atoms. In such lattices, the atoms are interconnected by very strong covalent bonds. An example of substances with this type of crystal lattice is diamond, one of the allotropic modifications of carbon.
Most substances with an atomic crystal lattice have very high melting points (for example, for diamond it is above $3500°C$), they are strong and hard, practically insoluble.
Molecular crystal lattices.
Molecular called crystal lattices, at the nodes of which molecules are located. Chemical bonds in these molecules can be either polar ($HCl, H_2O$) or nonpolar ($N_2, O_2$). Despite the fact that the atoms within the molecules are bound by very strong covalent bonds, there are weak forces of intermolecular attraction between the molecules themselves. Therefore, substances with molecular crystal lattices have low hardness, low melting points, and are volatile. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).
Metallic crystal lattices.
Substances with a metallic bond have metallic crystal lattices. At the nodes of such lattices there are atoms and ions (either atoms or ions, into which metal atoms easily turn, giving their outer electrons “for common use”). Such an internal structure of metals determines their characteristic physical properties: malleability, plasticity, electrical and thermal conductivity, and a characteristic metallic luster.
Molecular and non-molecular structure of substances. The structure of matter
It is not individual atoms or molecules that enter into chemical interactions, but substances. Substances are distinguished by the type of bond molecular and non-molecular structure. Substances made up of molecules are called molecular substances. The bonds between molecules in such substances are very weak, much weaker than between atoms inside a molecule, and already at relatively low temperatures they break - the substance turns into a liquid and then into a gas (iodine sublimation). The melting and boiling points of substances consisting of molecules increase with increasing molecular weight. To molecular substances include substances with an atomic structure (C, Si, Li, Na, K, Cu, Fe, W), among them there are metals and non-metals. To substances non-molecular structure include ionic compounds. Most compounds of metals with non-metals have this structure: all salts (NaCl, K 2 SO 4), some hydrides (LiH) and oxides (CaO, MgO, FeO), bases (NaOH, KOH). Ionic (non-molecular) substances have high melting and boiling points.
Solids: amorphous and crystalline
Solids are divided into crystalline and amorphous.
Amorphous substances do not have a clear melting point - when heated, they gradually soften and become fluid. In the amorphous state, for example, are plasticine and various resins.
Crystalline substances are characterized by the correct arrangement of the particles of which they are composed: atoms, molecules and ions - at strictly defined points in space. When these points are connected by straight lines, a spatial frame is formed, called the crystal lattice. The points at which crystal particles are located are called lattice nodes. Depending on the type of particles located at the nodes of the crystal lattice, and the nature of the connection between them, four types of crystal lattices are distinguished: ionic, atomic, molecular and metallic.
Crystal lattices are called ionic, at the sites of which there are ions. They are formed by substances with an ionic bond, which can be associated with both simple ions Na +, Cl -, and complex SO 4 2-, OH -. Consequently, salts, some oxides and hydroxides of metals have ionic crystal lattices. For example, a sodium chloride crystal is built from alternating positive Na + and negative Cl - ions, forming a cube-shaped lattice. The bonds between ions in such a crystal are very stable. Therefore, substances with an ionic lattice are characterized by relatively high hardness and strength, they are refractory and non-volatile.
Crystal lattice - a) and amorphous lattice - b).
Crystal lattice - a) and amorphous lattice - b). Atomic crystal lattices
nuclear called crystal lattices, in the nodes of which there are individual atoms. In such lattices, atoms are connected to each other very strong covalent bonds. An example of substances with this type of crystal lattice is diamond, one of the allotropic modifications of carbon. Most substances with an atomic crystal lattice have very high melting points (for example, in diamond it is over 3500 ° C), they are strong and hard, practically insoluble.
Molecular crystal lattices
Molecular called crystal lattices, at the nodes of which molecules are located. Chemical bonds in these molecules can be both polar (HCl, H 2 O) and non-polar (N 2 , O 2). Despite the fact that atoms within molecules are bound by very strong covalent bonds, weak forces of intermolecular attraction act between the molecules themselves. Therefore, substances with molecular crystal lattices have low hardness, low melting points, and are volatile. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).
Molecular crystal lattice (carbon dioxide) Metallic crystal lattices
Substances with metallic bond have metallic crystal lattices. At the nodes of such lattices are atoms and ions(either atoms, or ions, into which metal atoms easily turn, giving their outer electrons “for general use”). Such an internal structure of metals determines their characteristic physical properties: malleability, plasticity, electrical and thermal conductivity, and a characteristic metallic luster.
cheat sheets
A molecule in which the centers of gravity of the positively and negatively charged sections do not coincide is called a dipole. Let's define the concept of "dipole".
A dipole is a collection of two equal electric charges of opposite magnitude located at some distance from each other.
The hydrogen molecule H 2 is not a dipole (Fig. 50 a), and the hydrogen chloride molecule is a dipole (Fig. 50 b). The water molecule is also a dipole. The electron pairs in H 2 O are shifted to a greater extent from the hydrogen atoms to the oxygen atom.
The center of gravity of the negative charge is located near the oxygen atom, and the center of gravity of the positive charge is located near the hydrogen atoms.
In a crystalline substance, atoms, ions or molecules are in a strict order.
The place where such a particle is located is called node of the crystal lattice. The position of atoms, ions or molecules in the nodes of the crystal lattice is shown in fig. 51.
in g
Rice. 51. Models of crystal lattices (one plane of a bulk crystal is shown): a) covalent or atomic (diamond C, silicon Si, quartz SiO 2); b) ionic (NaCl); in) molecular (ice, I 2); G) metallic (Li, Fe). In the metal lattice model, dots denote electrons
According to the type of chemical bond between particles, crystal lattices are divided into covalent (atomic), ionic and metallic. There is another type of crystal lattice - molecular. In such a lattice, individual molecules are held by forces of intermolecular attraction.
Ionic crystals(Fig. 51 b) contain positively and negatively charged ions at the sites of the crystal lattice. The crystal lattice is constructed in such a way that the forces of electrostatic attraction of oppositely charged ions and the repulsive forces of like-charged ions are balanced. Such crystal lattices are characteristic of compounds such as LiF, NaCl, and many others.
molecular crystals(Fig. 51 in) contain dipole molecules at the sites of the crystal, which are held relative to each other by electrostatic attraction forces like ions in an ionic crystal lattice. For example, ice is a molecular crystal lattice formed by water dipoles. On fig. 51 in the symbols are not given for the charges, so as not to overload the figure.
metal crystal(Fig. 51 G) contains positively charged ions at the lattice sites. Some of the outer electrons move freely between the ions. " e-gas"holds positively charged ions in the nodes of the crystal lattice .. Upon impact, the metal does not prick like ice, quartz or a salt crystal, but only changes shape. Electrons, due to their mobility, have time to move at the moment of impact and keep ions in a new position. That is why forging metals and plastic, bend without breaking.
Rice. 52. The structure of silicon oxide: a) crystalline; b) amorphous. Black dots denote silicon atoms, open circles denote oxygen atoms. The plane of the crystal is depicted, so the fourth bond at the silicon atom is not indicated. The dashed line marks the short-range order in the disorder of an amorphous substance
In an amorphous substance, the three-dimensional periodicity of the structure, which is characteristic of the crystalline state, is violated (Fig. 52 b).
Liquids and gases differ from crystalline and amorphous bodies by the random movement of atoms and
molecules. In liquids, attractive forces are able to hold microparticles relative to each other at close distances, commensurate with the distances in a solid body. In gases, the interaction of atoms and molecules is practically absent, therefore, gases, unlike liquids, occupy the entire volume provided to them. A mole of liquid water at 100 0 C occupies a volume of 18.7 cm 3, and a mole of saturated water vapor 30,000 cm 3 at the same temperature. 
Rice. 53. Different types of interaction of molecules in liquids and gases: a) dipole–dipole; b) dipole–non-dipole; in) non-dipole–non-dipole
Unlike solids, molecules in liquids and gases move freely. As a result of the movement, they are oriented in a certain way. For example, in fig. 53 a,b. it is shown how dipole molecules interact, as well as non-polar molecules with dipole molecules in liquids and gases.
When a dipole approaches a dipole, the molecules rotate as a result of attraction and repulsion. The positively charged part of one molecule is located near the negatively charged part of another. This is how dipoles interact in liquid water.
When two non-polar molecules (non-dipoles) approach each other at fairly close distances, they also mutually influence each other (Fig. 53 in). Molecules are brought together by negatively charged electron shells covering the nuclei. The electron shells are deformed in such a way that there is a temporary appearance of positive and negative centers in either molecule, and they are mutually attracted to each other. It is enough for the molecules to disperse, as temporary dipoles again become non-polar molecules.
An example is the interaction between molecules of gaseous hydrogen. (Fig. 53 in).
3.2. Classification of inorganic substances. Simple and complex substances
At the beginning of the 19th century, the Swedish chemist Berzelius proposed that substances obtained from living organisms be called organic. Substances characteristic of inanimate nature were named inorganic or mineral(derived from minerals).
All solid, liquid and gaseous substances can be divided into simple and complex.
Substances are called simple, consisting of atoms of one chemical element.
For example, hydrogen, bromine and iron at room temperature and atmospheric pressure are simple substances that are respectively in gaseous, liquid and solid states (Fig. 54 a B C).
Gaseous hydrogen H 2 (g) and liquid bromine Br 2 (l) consist of diatomic molecules. Solid iron Fe(t) exists in the form of a crystal with a metallic crystal lattice.
Simple substances are divided into two groups: non-metals and metals.
a) b) in)
Rice. 54. Simple substances: a) gaseous hydrogen. It is lighter than air, so the test tube is stoppered and turned upside down; b) liquid bromine (usually stored in sealed ampoules); in) iron powder
Non-metals are simple substances with a covalent (atomic) or molecular crystal lattice in the solid state.
At room temperature, a covalent (atomic) crystal lattice is characteristic of such non-metals as boron B(t), carbon C(t), silicon Si(t). The molecular crystal lattice has white phosphorus P (t), sulfur S (t), iodine I 2 (t). Some non-metals only at very low temperatures pass into a liquid or solid state of aggregation. Under normal conditions, they are gases. Such substances include, for example, hydrogen H 2 (g), nitrogen N 2 (g), oxygen O 2 (g), fluorine F 2 (g), chlorine Cl 2 (g), helium He (g), neon Ne (d), argon Ar(d). At room temperature, molecular bromine Br 2 (l) exists in liquid form.
Metals are simple substances with a metallic crystal lattice in the solid state.
These are malleable, ductile substances that have a metallic luster and are capable of conducting heat and electricity.
Approximately 80% of the elements of the Periodic system form simple substances-metals. At room temperature, metals are solids. For example, Li(t), Fe(t). Only mercury, Hg (l) is a liquid that solidifies at -38.89 0 С.
Compounds are substances that are made up of atoms of different chemical elements.
The atoms of elements in a complex substance are connected by constant and well-defined relationships.
For example, water H 2 O is a complex substance. Its molecule contains atoms of two elements. Water always, anywhere on Earth contains 11.1% hydrogen and 88.9% oxygen by mass.
Depending on the temperature and pressure, water can be in a solid, liquid or gaseous state, which is indicated to the right of the chemical formula of the substance - H 2 O (g), H 2 O (g), H 2 O (t).
In practice, we, as a rule, deal not with pure substances, but with their mixtures.
A mixture is a collection of chemical compounds of different composition and structure
Let's represent simple and complex substances, as well as their mixtures in the form of a diagram:
Simple
non-metals
emulsions
Foundations
Complex substances in inorganic chemistry are divided into oxides, bases, acids and salts.
oxides
There are oxides of metals and non-metals. Metal oxides are compounds with ionic bonds. In the solid state, they form ionic crystal lattices.
Non-metal oxides- compounds with covalent chemical bonds.
Oxides are complex substances consisting of atoms of two chemical elements, one of which is oxygen, the oxidation state of which is -2.
Below are the molecular and structural formulas of some oxides of non-metals and metals.
Molecular formula Structural formula
CO 2 - carbon monoxide (IV) O \u003d C \u003d O
SO 2 - sulfur oxide (IV)
SO 3 - sulfur oxide (VI)
SiO 2 - silicon oxide (IV)
Na 2 O - sodium oxide
CaO - calcium oxide
K 2 O - potassium oxide, Na 2 O - sodium oxide, Al 2 O 3 - aluminum oxide. Potassium, sodium and aluminum form one oxide each.
If an element has several oxidation states, there are several of its oxides. In this case, after the name of the oxide, the degree of oxidation of the element is indicated by a Roman numeral in brackets. For example, FeO is iron (II) oxide, Fe 2 O 3 is iron (III) oxide.
In addition to the names formed according to the rules of international nomenclature, traditional Russian names for oxides are used, for example: CO 2 carbon monoxide (IV) - carbon dioxide, CO carbon monoxide (II) – carbon monoxide, CaO calcium oxide - quicklime, SiO 2 silicon oxide– quartz, silica, sand.
There are three groups of oxides, differing in chemical properties, - basic, acidic and amphoteric(other Greek , - both of them, dual).
Basic oxides formed by elements of the main subgroups of groups I and II of the Periodic system (the oxidation state of the elements is +1 and +2), as well as elements of secondary subgroups, the oxidation state of which is also +1 or +2. All of these elements are metals, so basic oxides are metal oxides, for example:
Li 2 O - lithium oxide
MgO - magnesium oxide
CuO - copper (II) oxide
Basic oxides correspond to bases.
Acid oxides
formed by non-metals and metals, the oxidation state of which is greater than +4, for example:
CO 2 - carbon monoxide (IV)
SO 2 - sulfur oxide (IV)
SO 3 - sulfur oxide (VI)
P 2 O 5 - phosphorus oxide (V)
Acid oxides correspond to acids.
Amphoteric oxides
formed by metals, the oxidation state of which is +2, +3, sometimes +4, for example:
ZnO - zinc oxide
Al 2 O 3 - aluminum oxide
Amphoteric oxides correspond to amphoteric hydroxides.
In addition, there is a small group of so-called indifferent oxides:
N 2 O - nitric oxide (I)
NO - nitric oxide (II)
CO - carbon monoxide (II)
It should be noted that one of the most important oxides on our planet is hydrogen oxide, known to you as water H 2 O.
Foundations
In the "Oxides" section, it was mentioned that bases correspond to basic oxides:
Sodium oxide Na 2 O - sodium hydroxide NaOH.
Calcium oxide CaO - calcium hydroxide Ca (OH) 2.
Copper oxide CuO - copper hydroxide Cu (OH) 2
Bases are complex substances consisting of a metal atom and one or more hydroxo groups -OH.
Bases are solids with an ionic crystal lattice.
When dissolved in water, crystals of soluble bases ( alkalis) are destroyed by the action of polar water molecules, and ions are formed:
NaOH(t) Na + (solution) + OH - (solution)
A similar record of ions: Na + (solution) or OH - (solution) means that the ions are in solution.
Foundation name includes the word hydroxide and the Russian name of the metal in the genitive case. For example, NaOH is sodium hydroxide, Ca (OH) 2 is calcium hydroxide.
If the metal forms several bases, then the oxidation state of the metal is indicated in the name with a Roman numeral in brackets. For example: Fe (OH) 2 - iron (II) hydroxide, Fe (OH) 3 - iron (III) hydroxide.
In addition, there are traditional names for some grounds:
NaOH- caustic soda, caustic soda
KOH - caustic potash
Ca (OH) 2 - slaked lime, lime water
R
Water-soluble bases are called alkalis
Distinguish soluble and insoluble bases in water.
These are metal hydroxides of the main subgroups of groups I and II, except for the hydroxides of Be and Mg.
Amphoteric hydroxides include,
HCl (g) H + (solution) + Cl - (solution)
Acids are called complex substances, which include hydrogen atoms that can be replaced or exchanged for metal atoms, and acid residues.
Depending on the presence or absence of oxygen atoms in the molecule, anoxic and oxygen-containing acids.
To name oxygen-free acids, a letter is added to the Russian name of a non-metal - about- and the word hydrogen :
HF - hydrofluoric acid
HCl - hydrochloric acid
HBr - hydrobromic acid
HI - hydroiodic acid
H 2 S - hydrosulfide acid
Traditional names for some acids:
HCl- hydrochloric acid; HF- hydrofluoric acid
To name oxygen-containing acids, endings are added to the root of the Russian name of a non-metal - naya,
-ovaya if the non-metal is in the highest oxidation state. The highest oxidation state coincides with the number of the group in which the non-metal element is located:
H 2 SO 4 - ser naya acid
HNO 3 - nitrogen naya acid
HClO 4 - chlorine naya acid
HMnO 4 - manganese new acid
If an element forms acids in two oxidation states, then the ending is used to name the acid corresponding to the lower oxidation state of the element - true:
H 2 SO 3 - chamois true acid
HNO 2 - nitrogen true acid
According to the number of hydrogen atoms in a molecule, monobasic(HCl, HNO 3), dibasic(H 2 SO 4), tribasic acids (H 3 PO 4).
Many oxygen-containing acids are formed by the interaction of the corresponding acidic oxides with water. The oxide corresponding to a given acid is called its anhydride:
Sulfur dioxide SO 2 - sulfurous acid H 2 SO 3
Sulfuric anhydride SO 3 - sulfuric acid H 2 SO 4
Nitrous anhydride N 2 O 3 - nitrous acid HNO 2
Nitric anhydride N 2 O 5 - nitric acid HNO 3
Phosphoric anhydride P 2 O 5 - phosphoric acid H 3 PO 4
Note that the oxidation states of an element in the oxide and the corresponding acid are the same.
If an element in the same oxidation state forms several oxygen-containing acids, then the prefix "" is added to the name of the acid with a lower content of oxygen atoms. meta", with high oxygen content - prefix " ortho". For example:
HPO 3 - metaphosphoric acid
H 3 PO 4 - orthophosphoric acid, which is often referred to simply as phosphoric acid
H 2 SiO 3 - metasilicic acid, usually called silicic acid
H 4 SiO 4 - orthosilicic acid.
Silicic acids are not formed by the interaction of SiO 2 with water, they are obtained in a different way.
FROM
Salts are complex substances consisting of metal atoms and acidic residues.
oli
NaNO 3 - sodium nitrate
CuSO 4 - copper sulfate (II)
CaCO 3 - calcium carbonate
When dissolved in water, salt crystals are destroyed, ions are formed:
NaNO 3 (t) Na + (solution) + NO 3 - (solution).
Salts can be considered as products of complete or partial replacement of hydrogen atoms in an acid molecule by metal atoms, or as products of complete or partial replacement of base hydroxo groups by acidic residues.
With the complete replacement of hydrogen atoms, medium salts: Na 2 SO 4, MgCl 2. . With partial substitution, acid salts (hydrosalts) NaHSO4 and basic salts (hydroxosalts) MgOHCl.
According to the rules of international nomenclature, the names of salts are formed from the name of the acid residue in the nominative case and the Russian name of the metal in the genitive case (Table 12):
NaNO 3 - sodium nitrate
CuSO 4 - copper(II) sulfate
CaCO 3 - calcium carbonate
Ca 3 (RO 4) 2 - calcium orthophosphate
Na 2 SiO 3 - sodium silicate
The name of the acid residue is derived from the root of the Latin name of the acid-forming element (for example, nitrogenium - nitrogen, the root nitr-) and the endings:
-at for the highest oxidation state, -it for a lower oxidation state of the acid-forming element (Table 12).
Table 12
Names of acids and salts
| Name of the acid | Acid Formula | The name of the salts | Examples Soleil |
| Hydrogen chloride (salt) | HCl | chlorides | AgCl silver chloride |
| Hydrogen sulfide | H 2 S | Sulfides | FeS Sulf id iron(II) |
| sulphurous | H2SO3 | Sulfites | Na 2 SO 3 Sulf it sodium |
| sulfuric | H2SO4 | sulfates | K 2 SO 4 Sulf at potassium |
| nitrogenous | HNO 2 | Nitrites | LiNO 2 Nitr it lithium |
| Nitrogen | HNO3 | Nitrates | Al(NO 3) 3 Nitr at aluminum |
| orthophosphoric | H3PO4 | Orthophosphates | Ca 3 (PO 4) 2 Calcium orthophosphate |
| Coal | H2CO3 | Carbonates | Na 2 CO 3 Sodium carbonate |
| Silicon | H2SiO3 | silicates | Na 2 SiO 3 Sodium silicate |
NaHSO 4 - sodium hydrogen sulfate
NaHS - sodium hydrosulfide
The names of basic salts are formed by adding the prefix " hydroxo": MgOHCl - magnesium hydroxochloride.
In addition, many salts have traditional names, such as:
Na 2 CO 3 - soda;
NaHCO3 - food (drinking) soda;
CaCO 3 - chalk, marble, limestone.
