General scheme for the formation of a metal bond. Metal bond

A metallic bond occurs between metal atoms. A characteristic feature of metal atoms is a small number of electrons at the external energy level, weakly held by the nucleus, and a large number of free atomic orbitals with similar energies, so the metal bond is unsaturated.

Valence electrons participate in the formation of bonds with 8 or 12 atoms at once (in accordance with the coordination number of metal atoms). Under these conditions, valence electrons with a low ionization energy move along the accessible orbitals of all neighboring atoms, providing a bond between them.

Metal bond characterized by a weak interaction of common electrons with the nuclei of the connected atoms and the complete delocalization of these electrons between all atoms in the crystal, which ensures the stability of this bond.

Formation of a metal bond (M - metal):

М 0 - ne М n +

Metals have a special crystal lattice, in the nodes of which there are both neutral and positively charged metal atoms, between which socialized electrons ("electron gas") freely move (within the crystal). The movement of common electrons in metals is carried out along a multitude of molecular orbitals arising from the fusion of a large number of free orbitals of the joined atoms and covering many atomic nuclei. In the case of a metallic bond, it is impossible to speak of its direction, since the common electrons are uniformly delocalized throughout the crystal.

The structural features of metals determine their characteristic physical properties: hardness, malleability, high electrical and thermal conductivity, as well as a special metallic luster.

A metallic bond is characteristic of metals not only in a solid state, but also in a liquid state, that is, this is a property of atomic aggregates located in close proximity to each other. In a gaseous state, metal atoms are linked by one or more covalent bonds into molecules, for example, Li 2 (Li – Li), Be 2 (Be = Be), Al 4 - each aluminum atom is connected to three others to form a tetrahedral structure:

4. Hydrogen bond

A hydrogen bond is a special type of bond that is unique to hydrogen atoms. It occurs when a hydrogen atom is associated with an atom of the most electronegative elements, primarily fluorine, oxygen and nitrogen. Let us consider the formation of a hydrogen bond using the example of hydrogen fluoride. An electronegative hydrogen atom has only one electron, thanks to which it can form a covalent bond with a fluorine atom. In this case, a molecule of hydrogen fluoride H-F appears, in which the total electron pair is displaced towards the fluorine atom.

As a result of this electron density distribution, the hydrogen fluoride molecule is a dipole, the positive pole of which is a hydrogen atom. Due to the fact that the bonding electron pair is shifted towards the fluorine atom, it is partially released 1 s-orbital of the hydrogen atom and its nucleus is partially exposed. In any other atom, the positive charge of the nucleus, after the removal of valence electrons, is screened by the inner electron shells, which ensure the repulsion of the electron shells of other atoms. The hydrogen atom does not have such shells, its nucleus is a very small (subatomic) positively charged particle - a proton (the diameter of a proton is about 10 5 times smaller than the diameters of atoms, and, due to its lack of electrons, it is attracted by the electron shell of other electrically neutral or negatively charged atoms).

The strength of the electric field near a partially "naked" hydrogen atom is so great that it can actively attract the negative pole of a neighboring molecule. Since this pole is a fluorine atom, which has three non-bonding electron pairs, and s- the orbital of the hydrogen atom is partially vacant, then a donor-acceptor interaction occurs between the positively polarized hydrogen atom of one molecule and the negatively polarized fluorine atom of the neighboring molecule.

Thus, as a result of joint electrostatic and donor-acceptor interactions, an additional second bond arises with the participation of a hydrogen atom. That's what it is hydrogen bond, ... N – F N – F ...

It differs from covalent in energy and length. The hydrogen bond is longer and less strong than the covalent bond. The energy of the hydrogen bond is 8–40 kJ / mol, and that of the covalent bond is 80–400 kJ / mol. In solid hydrogen fluoride, the length of the H – F covalent bond is 95 pm, the length of the F H hydrogen bond is 156 pm. Due to the hydrogen bond between HF molecules, crystals of solid hydrogen fluoride consist of endless planar zigzag chains, since the system of three atoms formed due to the hydrogen bond is usually linear.

Hydrogen bonds between HF molecules are partially retained in liquid and even gaseous hydrogen fluoride.

The hydrogen bond is conventionally written in the form of three dots and is depicted as follows:

where X, Y are atoms F, O, N, Cl, S.

The energy and length of the hydrogen bond are determined by the dipole moment of the H – X bond and the size of the Y atom. The length of the hydrogen bond decreases, and its energy increases with an increase in the difference between the electronegativities of the X and Y atoms (and, accordingly, the dipole moment of the H – X bond) and with a decrease in the size of the Y atom ...

Hydrogen bonds are also formed between molecules in which there are O – H bonds (for example, water H 2 O, perchloric acid HClO 4, nitric acid HNO 3, carboxylic acids RCOOH, phenol C 6 H 5 OH, alcohols ROH) and N – H (eg ammonia NH 3, thiocyanic acid HNCS, organic amides RCONH 2 and amines RNH 2 and R 2 NH).

Substances whose molecules are connected by hydrogen bonds differ in their properties from substances similar to them in molecular structure, but do not form hydrogen bonds. The melting and boiling points of hydrides of group IVA elements, in which there are no hydrogen bonds, smoothly decrease with decreasing period number (Fig. 15). For hydrides of VA-VIIA elements, this dependence is violated. Three substances, the molecules of which are connected by hydrogen bonds (ammonia NH 3, water H 2 O and hydrogen fluoride HF), have much higher melting and boiling points than their counterparts (Fig. 15). In addition, these substances have wider temperature ranges of existence in the liquid state, higher heats of fusion and evaporation.

Hydrogen bond plays an important role in the processes of dissolution and crystallization of substances, as well as in the formation of crystalline hydrates.

A hydrogen bond can form not only between molecules (intermolecular hydrogen bond, MBC) , as is the case in the examples considered above, but also between the atoms of the same molecule (intramolecular hydrogen bond, VVS) . For example, due to intramolecular hydrogen bonds between the hydrogen atoms of the amino groups and the oxygen atoms of the carbonyl groups, the polypeptide chains that form the protein molecules have a helical shape.

drawing??????????????

Hydrogen bonds play a huge role in the processes of protein reduplication and biosynthesis. The two strands of the DNA double helix (deoxyribonucleic acid) are held together by hydrogen bonds. During the process of reduplication, these links are broken. During transcription, the synthesis of RNA (ribonucleic acid) using DNA as a template also occurs due to the occurrence of hydrogen bonds. Both processes are possible because hydrogen bonds are easily formed and easily broken.

Rice. 15. Melting points ( a) and boiling ( b) hydrides of elements of groups IVА-VIIА.

The purpose of the lesson

• Give an idea of ​​the metallic chemical bond.

• Learn to write down the formation of a metal bond.

• Get acquainted with the physical properties of metals.

• Learn to clearly distinguish types chemical bonds .

Lesson Objectives

• Learn how they interact with each other metal atoms

• Determine how the metal bond affects the properties of the substances formed by it

Basic terms:

• Electronegativity - the chemical property of an atom, which is a quantitative characteristic of the ability of an atom in a molecule to attract common electron pairs to itself.
• Chemical bond - the phenomenon of interaction of atoms, due to the overlap of electron clouds of interacting atoms.
• Metal bond - This is a bond in metals between atoms and ions, formed due to the socialization of electrons.
• Covalent bond - a chemical bond, formed by overlapping a pair of valence electrons. The electrons that provide the bond are called the common electron pair. There are 2 types: polar and non-polar.
• Ionic bond - a chemical bond that forms between atoms of non-metals, in which a common electron pair goes to an atom with greater electronegativity. As a result, atoms are attracted like oppositely charged bodies.
• Hydrogen bond - a chemical bond between an electronegative atom and a hydrogen atom H, covalently bonded to another electronegative atom. N, O, or F can act as electronegative atoms. Hydrogen bonds can be intermolecular or intramolecular.

  DURING THE CLASSES

Metallic chemical bond

Identify the items that are in the wrong "queue". Why?
Ca Fe P K Al Mg Na
Which elements from the table Mendeleev are called metals?
Today we will find out what properties metals have, and how they depend on the bond that is formed between metal ions.
To begin with, let's remember the location of metals in the periodic system?
Metals, as we all know, usually do not exist in the form of isolated atoms, but in the form of a lump, ingot or metal product. Let's find out what collects metal atoms in an integral volume.

In the example, we see a piece of gold. And by the way, gold is a unique metal. With the help of forging from pure gold, you can make foil with a thickness of 0.002 mm! Such a thin sheet of foil is almost transparent and has a green tint in the lumen. As a result, from an ingot of gold the size of a matchbox, you can get a thin foil that will cover the area of ​​the tennis court.
Chemically, all metals are characterized by the ease of giving up valence electrons, and as a result, the formation of positively charged ions and exhibit only positive oxidation. That is why free metals are reducing agents. A common feature of metal atoms is their large size relative to non-metals. External electrons are located at large distances from the nucleus and therefore are weakly bound to it, therefore they are easily torn off.
Atoms of a large amount of metals on the outer level have a small number of electrons - 1,2,3. These electrons are easily ripped off and the metal atoms become ions.
Ме0 - n ē ⇆ Men +
metal atoms - external electrons orbits ⇆ metal ions

Thus, the detached electrons can move from one ion to another, that is, they become free, and, as it were, connecting them into a single whole. Therefore, it turns out that all the detached electrons are common, since it is impossible to understand which electron belongs to which of the metal atoms.
Electrons can combine with cations, then atoms are temporarily formed, from which electrons are then torn away from sniffling. This process takes place continuously and without interruption. It turns out that in the bulk of the metal atoms are continuously transformed into ions and vice versa. In this case, a small number of common electrons bind a large number of metal atoms and ions. But it is important that the number of electrons in a metal is equal to the total charge of positive ions, that is, it turns out that the metal as a whole remains electrically neutral.
This process is presented as a model - metal ions are in a cloud of electrons. Such an electron cloud is called "electron gas".

For example, in this picture we see how the electrons move among the stationary ions inside the crystal lattice of metal.

Rice. 2. Electronic movement

In order to better understand what Electron Gas is and how it behaves in chemical reactions of different metals, we will watch an interesting video. (gold in this video is exclusively referred to as a color!)

Now we can write down the definition: a metallic bond is a bond in metals between atoms and ions, formed by the socialization of electrons.

Let's compare all the types of connections that we know And fix them in order to better distinguish them, for this we will watch the video.

Metallic bond occurs not only in pure metals, but also characteristic of mixtures of different metals, alloys in different states of aggregation.
The metallic bond is important and determines the basic properties of metals
- electrical conductivity - disorderly movement of electrons in the volume of the metal. But with a small potential difference, so that the electrons move in an orderly manner. The metals with the best conductivity are Ag, Cu, Au, Al.
- plasticity
The bonds between the metal layers are not very significant, this allows you to move the layers under load (deform the metal without breaking it). The best deformable metals (soft) Au, Ag, Cu.
- metallic luster
Electron gas reflects almost all light rays. This is why pure metals shine so strongly and are most often gray or white in color. Metals that are the best reflectors Ag, Cu, Al, Pd, Hg

Homework

Exercise 1
Choose formulas of substances that have
a) covalent polar bond: Cl2, KCl, NH3, O2, MgO, CCl4, SO2;
b) with ionic bond: HCl, KBr, P4, H2S, Na2O, CO2, CaS.
Exercise 2
Cross out the unnecessary:
a) CuCl2, Al, MgS
b) N2, HCl, O2
c) Ca, CO2, Fe
d) MgCl2, NH3, H2

Metallic sodium, metallic lithium, and other alkali metals change the color of the flame. Lithium metal and its salts give the fire a red color, metallic sodium and sodium salts - yellow, metallic potassium and its salts - purple, and rubidium and cesium - also purple, but lighter.

Rice. 4. A piece of metallic lithium

Rice. 5. Coloring the flame with metals

Lithium (Li). Lithium metal, like sodium metal, belongs to alkali metals. Both dissolve in water. Sodium dissolves in water and forms caustic soda, a very strong acid. When alkali metals dissolve in water, a lot of heat and gas (hydrogen) is released. It is advisable not to touch such metals with your hands, as you can get burned.

Bibliography

1. Lesson on the topic "Metallic chemical bond", teacher of chemistry Tukhta Valentina Anatolyevna MOU "Esenovichskaya secondary school"
2. F. A. Derkach "Chemistry" - scientific and methodological manual. - Kiev, 2008.
3. LB Tsvetkova "Inorganic Chemistry" - 2nd edition, revised and enlarged. - Lviv, 2006.
4. V. V. Malinovsky, P. G. Nagorny "Inorganic chemistry" - Kiev, 2009.
5. Glinka N.L. General chemistry. - 27th ed. / Under. ed. V.A. Rabinovich. - L .: Chemistry, 2008. - 704 pp.

Edited and sent by A.V. Lisnyak

Worked on the lesson:

Tukhta V.A.

Lisnyak A.V.

You can raise a question about modern education, express an idea or solve an urgent problem at Educational Forum where an educational council of fresh thought and action meets internationally. By creating blog, Chemistry grade 8

It is extremely rare that chemicals are composed of separate, unrelated atoms of chemical elements. Only a small number of gases called noble gases have such a structure under normal conditions: helium, neon, argon, krypton, xenon and radon. More often than not, chemical substances do not consist of scattered atoms, but of their associations in various groups. Such associations of atoms can number several units, hundreds, thousands, or even more atoms. The force that keeps these atoms in the composition of such groupings is called chemical bond.

In other words, we can say that a chemical bond is an interaction that provides a bond between individual atoms in more complex structures (molecules, ions, radicals, crystals, etc.).

The reason for the formation of a chemical bond is that the energy of more complex structures is less than the total energy of the individual atoms that form it.

So, in particular, if an XY molecule is formed during the interaction of atoms X and Y, this means that the internal energy of the molecules of this substance is lower than the internal energy of the individual atoms from which it was formed:

E (XY)< E(X) + E(Y)

For this reason, when chemical bonds form between individual atoms, energy is released.

The formation of chemical bonds is attended by the electrons of the outer electron layer with the lowest binding energy with the nucleus, called valence... For example, in boron, these are electrons of 2 energy levels - 2 electrons for 2 s- orbitals and 1 by 2 p-orbitals:

When a chemical bond is formed, each atom seeks to obtain an electronic configuration of atoms of noble gases, i.e. so that there are 8 electrons in its outer electron layer (2 for the elements of the first period). This phenomenon is called the octet rule.

Achievement of the electronic configuration of a noble gas by atoms is possible if initially single atoms make part of their valence electrons common to other atoms. In this case, common electron pairs are formed.

Depending on the degree of electron socialization, covalent, ionic and metallic bonds can be distinguished.

Covalent bond

A covalent bond occurs most often between the atoms of nonmetal elements. If the atoms of non-metals that form a covalent bond belong to different chemical elements, such a bond is called a covalent polar bond. The reason for this name lies in the fact that atoms of different elements also have a different ability to attract a common electron pair. Obviously, this leads to a displacement of the common electron pair towards one of the atoms, as a result of which a partial negative charge is formed on it. In turn, a partial positive charge is formed on the other atom. For example, in a hydrogen chloride molecule, an electron pair is displaced from a hydrogen atom to a chlorine atom:

Examples of substances with a covalent polar bond:

СCl 4, H 2 S, CO 2, NH 3, SiO 2, etc.

A covalent non-polar bond is formed between the atoms of non-metals of the same chemical element. Since the atoms are identical, their ability to pull off shared electrons is the same. In this regard, the displacement of the electron pair is not observed:

The above mechanism for the formation of a covalent bond, when both atoms provide electrons for the formation of common electron pairs, is called exchange.

There is also a donor-acceptor mechanism.

When a covalent bond is formed by the donor-acceptor mechanism, a common electron pair is formed due to the filled orbital of one atom (with two electrons) and the empty orbital of another atom. An atom providing a lone electron pair is called a donor, and an atom with a free orbital is called an acceptor. Atoms with paired electrons act as donors of electron pairs, for example, N, O, P, S.

For example, according to the donor-acceptor mechanism, the fourth covalent N-H bond is formed in the ammonium cation NH 4 +:

In addition to polarity, covalent bonds are also characterized by energy. Bond energy is the minimum energy required to break a bond between atoms.

The binding energy decreases with an increase in the radii of the bonded atoms. Since, as we know, atomic radii increase downward along subgroups, one can, for example, conclude that the strength of the halogen-hydrogen bond increases in the series:

HI< HBr < HCl < HF

Also, the bond energy depends on its multiplicity - the greater the bond multiplicity, the more its energy. The bond multiplicity refers to the number of common electron pairs between two atoms.

Ionic bond

The ionic bond can be considered as the limiting case of the covalent polar bond. If in a covalent-polar bond the total electron pair is partially displaced to one of the pair of atoms, then in the ionic it is almost completely "given" to one of the atoms. The atom that donated the electron (s) acquires a positive charge and becomes cation, and the atom, which took the electrons from it, acquires a negative charge and becomes anion.

Thus, an ionic bond is a bond formed due to the electrostatic attraction of cations to anions.

The formation of this type of bond is characteristic of the interaction of atoms of typical metals and typical non-metals.

For example, potassium fluoride. The potassium cation is obtained as a result of the abstraction of one electron from the neutral atom, and the fluorine ion is formed when one electron is attached to the fluorine atom:

A force of electrostatic attraction arises between the resulting ions, as a result of which an ionic compound is formed.

During the formation of a chemical bond, electrons from the sodium atom passed to the chlorine atom and oppositely charged ions were formed, which have a complete external energy level.

It was found that electrons are not completely detached from the metal atom, but only displaced towards the chlorine atom, as in a covalent bond.

Most binary compounds that contain metal atoms are ionic. For example, oxides, halides, sulfides, nitrides.

An ionic bond also occurs between simple cations and simple anions (F -, Cl -, S 2-), as well as between simple cations and complex anions (NO 3 -, SO 4 2-, PO 4 3-, OH -). Therefore, salts and bases (Na 2 SO 4, Cu (NO 3) 2, (NH 4) 2 SO 4), Ca (OH) 2, NaOH) are referred to ionic compounds.

Metal bond

This type of bond is formed in metals.

The atoms of all metals have electrons on the outer electron layer, which have a low binding energy with the atomic nucleus. For most metals, the process of loss of external electrons is energetically favorable.

Due to such a weak interaction with the nucleus, these electrons in metals are very mobile and the following process continuously occurs in each metal crystal:

M 0 - ne - = M n +, where M 0 is a neutral metal atom, and M n + is a cation of the same metal. The figure below provides an illustration of the ongoing processes.

That is, electrons "carry" along the metal crystal, detaching from one metal atom, forming a cation from it, joining another cation, forming a neutral atom. This phenomenon was called "electronic wind", and the set of free electrons in a crystal of a non-metal atom was called "electron gas". This type of interaction between metal atoms is called a metal bond.

Hydrogen bond

If a hydrogen atom in any substance is associated with an element with high electronegativity (nitrogen, oxygen or fluorine), such a substance is characterized by such a phenomenon as a hydrogen bond.

Since a hydrogen atom is bonded to an electronegative atom, a partial positive charge is formed on the hydrogen atom, and a partial negative charge on the electronegative element. In this regard, electrostatic attraction becomes possible between the partially positively charged hydrogen atom of one molecule and the electronegative atom of another. For example, a hydrogen bond is observed for water molecules:

It is the hydrogen bond that explains the abnormally high melting point of water. In addition to water, strong hydrogen bonds are also formed in substances such as hydrogen fluoride, ammonia, oxygen-containing acids, phenols, alcohols, and amines.

A metallic bond is a chemical bond caused by the presence of relatively free electrons. It is typical for both pure metals and their alloys and intermetallic compounds.

Metal link mechanism

Positive metal ions are located at all nodes of the crystal lattice. Between them, valence electrons, detached from atoms during the formation of ions, move randomly, like gas molecules. These electrons act as cement, holding the positive ions together; otherwise, the lattice would disintegrate under the action of the repulsive forces between the ions. At the same time, electrons are held by ions within the crystal lattice and cannot leave it. Communication forces are not localized and directed.

Therefore, in most cases, high coordination numbers appear (for example, 12 or 8). When two metal atoms come together, the orbitals of their outer shells overlap to form molecular orbitals. If a third atom comes up, its orbital overlaps with the orbitals of the first two atoms, which gives another molecular orbital. When there are many atoms, a huge number of three-dimensional molecular orbitals arise, stretching in all directions. Due to the multiple overlapping of the orbitals, the valence electrons of each atom are influenced by many atoms.

Characteristic crystal lattices

Most metals form one of the following highly symmetric close-packed lattices: body-centered cubic, face-centered cubic, and hexagonal.

In a cubic body-centered lattice (BCC), atoms are located at the vertices of the cube and one atom in the center of the volume of the cube. Metals have a cubic body-centered lattice: Pb, K, Na, Li, β-Ti, β-Zr, Ta, W, V, α-Fe, Cr, Nb, Ba, etc.

In a face-centered cubic lattice (FCC), atoms are located at the vertices of the cube and at the center of each face. Metals of this type have a lattice: α-Ca, Ce, α-Sr, Pb, Ni, Ag, Au, Pd, Pt, Rh, γ-Fe, Cu, α-Co, etc.

In a hexagonal lattice, atoms are located at the vertices and center of the hexagonal bases of the prism, and three atoms are located in the middle plane of the prism. Metals have such a packing of atoms: Mg, α-Ti, Cd, Re, Os, Ru, Zn, β-Co, Be, β-Ca, etc.

Other properties

Freely moving electrons provide high electrical and thermal conductivity. Substances with a metallic bond often combine strength with ductility, since when atoms are displaced relative to each other, the bonds do not break. Metallic aroma is also an important property.

Metals conduct heat and electricity well, they are strong enough, they can be deformed without destruction. Some metals are malleable (they can be forged), some are ductile (they can be pulled out of wire). These unique properties are explained by a special type of chemical bond that connects metal atoms to each other - a metal bond.

Metals in the solid state exist in the form of crystals of positive ions, as if “floating” in the sea of ​​electrons freely moving between them.

The metallic bond explains the properties of metals, in particular their strength. Under the action of the deforming force, the metal lattice can change its shape without cracking, in contrast to ionic crystals.

The high thermal conductivity of metals is explained by the fact that if a piece of metal is heated on one side, the kinetic energy of the electrons will increase. This increase in energy will propagate in the "electron sea" throughout the sample at great speed.

The electrical conductivity of metals also becomes clear. If a potential difference is applied to the ends of a metal sample, then the cloud of delocalized electrons will shift in the direction of the positive potential: this flow of electrons moving in one direction is the familiar electric current.

Only noble gases are found in a monatomic state under normal conditions. The rest of the elements do not exist as an individual, since they have the ability to interact with each other or with other atoms. This produces more complex particles.

In contact with

A set of atoms can form the following particles:

• molecules;
• molecular ions;
• free radicals.

Types of chemical interactions

The interaction between atoms is called a chemical bond. The basis is electrostatic forces (forces of interaction of electric charges) that act between atoms, the carriers of these forces are the nucleus of the atom and electrons.

The electrons located on the external energy level are assigned the main role in the formation of chemical bonds between atoms. They are the farthest from the nucleus, and, therefore, are least strongly connected to it. They are called valence electrons.

The particles interact with each other in various ways, which leads to the formation of molecules (and substances) of different structures. The following types of chemical bonds are distinguished:

• ionic;
• covalent;
• van der Waals;
• metal.

When talking about the different types of chemical interactions between atoms, it is worth remembering that all types are equally based on the electrostatic interaction of particles.

Metallic chemical bond

As can be seen from the position of metals in the table of chemical elements, they, for the most part, have a small number of valence electrons. Electrons are bound to their nuclei rather weakly and easily detach from them. As a result, positively charged metal ions and free electrons are formed.

These electrons, freely moving in the crystal lattice, are called "electron gas".

The figure schematically shows the structure of a metal substance.

That is, in the bulk of the metal, atoms are constantly transformed into ions (they are called atom-ions) and vice versa, ions are constantly receiving electrons from the "electron gas".

The mechanism for the formation of a metal bond can be written in the form of the formula:

atom M 0 - ne ↔ ion M n +

Thus, metals are positive ions, which are located in the crystal lattice in certain positions, and electrons, which can move quite freely between atom-ions.

Crystalline grid represents the "skeleton", the skeleton of matter, and electrons move between its nodes. The forms of crystal lattices of metals can be different, for example:

• the volume-centric cubic lattice is typical for alkali metals;
• face-centered cubic lattice have, for example, zinc, aluminum, copper, other transition elements;
• the hexagonal shape is typical for alkaline earth elements (barium is an exception);
• tetragonal structure - in indium;
• rhombohedral - for mercury.

An example of a crystal lattice of a metal is shown in the picture below..

Differences from other species

The metallic bond differs from the covalent bond in strength. The energy of metallic bonds is less than covalent by 3-4 times and less ionic bond energy.

In the case of a metal bond, one cannot speak of directionality, the covalent bond is strictly directed in space.

Such a characteristic as saturation is also not typical for the interaction between metal atoms. While covalent bonds are saturable, that is, the number of atoms with which interaction can occur is strictly limited by the number of valence electrons.

Communication diagram and examples

The process taking place in metal can be written using the formula:

K - e<->K +

Al - 3e<->Al 3+

Na - e<->Na +

Zn - 2e<->Zn 2+

Fe - 3e<->Fe 3+

If we describe in more detail, the metallic bond, how this type of bond is formed, it is necessary to consider the structure of the external energy levels of the element.

Consider sodium as an example. The only 3s valence electron available on the external level can freely move along the free orbitals of the third energy level. As the sodium atoms approach each other, the orbitals overlap. Now all electrons can move between atom-ions within the limits of all interrupted orbitals.

For zinc, for 2 valence electrons, there are as many as 15 free orbitals at the fourth energy level. When atoms interact, these free orbitals will overlap, as if socializing the electrons that move along them.

Chromium atoms have 6 valence electrons, and all of them will participate in the formation of an electron gas and bind atom-ions.

A special type of interaction, which is characteristic of metal atoms, determines a number of properties that unite them and distinguish metals from other substances. Examples of such properties are high melting points, high boiling points, malleability, ability to reflect light, high electrical conductivity and thermal conductivity.

The high melting and boiling points are explained by the fact that the metal cations are tightly bound by the electron gas. At the same time, there is a pattern that the bond strength increases with an increase in the number of valence electrons. For example, rubidium and potassium are fusible substances (melting points 39 and 63 degrees Celsius, respectively), compared to, for example, chromium (1615 degrees Celsius).

The uniformity of the distribution of valence electrons over the crystal explains, for example, such a property of metals as plasticity - the displacement of ions and atoms in any direction without destroying the interaction between them.

The free movement of electrons in atomic orbitals also explains the electrical conductivity of metals. Electron gas with superimposed difference potentials passes from chaotic motion to directional motion.

In industry, not pure metals are often used, but their mixtures, called alloys. In an alloy, the properties of one component usually complement the properties of the other.

The metallic type of interaction is characteristic both for pure metals and for their mixtures - alloys in solid and liquid states. However, if the metal is transferred to a gaseous state, then the bond between its atoms will be covalent. Metal in the form of a vapor also consists of individual molecules (mono- or diatomic).