Metal bond: the mechanism of education. Metal chemical bonds: examples

All known chemical elements located in the periodic table are divided into two groups: metals and nonmetals. In order for them to become not just elements, but compounds, chemicals, they can interact with each other, they must exist in the form of simple and complex substances.

It is for this purpose that some electrons try to accept, and others - to give. Replacing each other in this way, the elements form different chemical molecules. But what allows them to hold together? Why are there substances of such strength, which can not be destroyed even by the most serious tools? And others, on the contrary, are destroyed by the slightest influence. All this is explained by the formation of various types of chemical bonds between atoms in molecules, the formation of a crystal lattice of a certain structure.

Types of chemical bonds in compounds

In total, there are 4 main types of chemical bonds.

1. Covalent nonpolar. It is formed between two identical nonmetals due to the socialization of electrons, the formation of common electronic pairs. Valence unpaired particles take part in its formation. Examples: halogens, oxygen, hydrogen, nitrogen, sulfur, phosphorus.
2. Covalent polar. It is formed between two different non-metals, or between a metal that is very weak in properties and a non-metal weak in electronegativity. The basis is also common electronic pairs and their tugging to themselves by that atom whose affinity to the electron is higher. Examples: NH _3, SiC, P ₂ O ₅ and others.
3. Hydrogen bond. The most unstable and weak, is formed between the strongly electronegative atom of one molecule and the positive one. Most often this happens when the substances are dissolved in water (alcohol, ammonia, and so on). Thanks to such a connection, there may exist macromolecules of proteins, nucleic acids, complex carbohydrates, and so on.
4. Ionic bonding. It is formed due to the forces of electrostatic attraction of differently charged metal ions and nonmetals. The stronger the difference in this indicator, the more pronounced is the ionic character of the interaction. Examples of compounds: binary salts, complex compounds - bases, salts.
5. The metal bond, the mechanism of formation of which, as well as the properties, will be considered further. It is formed in metals, their alloys of various kinds.

There is such a thing as the unity of the chemical bond. It just says that it is impossible to consider each chemical bond as a reference. They are all conditionally designated units. After all, the basis of all interactions is a single principle - the electron-static interaction. Therefore, the ionic, metallic, covalent bond and hydrogen bond have a single chemical nature and are only boundary cases of each other.

Metals and their physical properties

Metals are in the vast majority of all chemical elements. This is due to their special properties. A significant part of them was obtained by man by nuclear reactions in the laboratory, they are radioactive with a short half-life.

However, most are natural elements that form whole rocks and ores, are part of most important compounds. It is from them that people learned to cast alloys and make a lot of beautiful and important products. These are such as copper, iron, aluminum, silver, gold, chrome, manganese, nickel, zinc, lead and many others.

For all metals, it is possible to single out general physical properties, which explains the scheme for the formation of a metal bond. What are these properties?

1. Kovkost and plasticity. It is known that many metals can be rolled even to the state of the foil (gold, aluminum). Of the others, wire, metal flexible sheets, articles capable of deforming under physical influence, but then immediately recover the shape after stopping it. It is these qualities of metals that are called ductility and plasticity. The reason for this feature is the metallic type of connection. The ions and electrons in the crystal slide relative to each other without breaking, which allows preserving the integrity of the entire structure.
2. Metallic shine. This also explains the metal bond, the mechanism of education, its characteristics and features. Thus, not all particles are capable of absorbing or reflecting light waves of equal length. Atoms of most metals reflect short-wave rays and acquire almost the same color silver, white, pale bluish hue. Exceptions are copper and gold, their color is reddish-red and yellow, respectively. They are capable of reflecting longer wavelength radiation.
3. Heat and electrical conductivity. These properties are also explained by the structure of the crystal lattice and the fact that in its formation a metallic type of bond is realized. Due to the "electronic gas" moving inside the crystal, the electric current and heat are instantaneously and evenly distributed between all atoms and ions and are conducted through the metal.
4. Solid state under normal conditions. Here the only exception is mercury. All other metals are necessarily strong, solid compounds, as well as their alloys. This is also the result of the presence of metal bonds in metals. The mechanism of formation of this type of particle binding completely confirms the properties.

These are the basic physical characteristics for metals, which explains and determines precisely the scheme for the formation of a metal bond. Such a method of joining atoms for metal elements and their alloys is actual. That is for them in a solid and liquid state.

Metal type of chemical bond

What is its peculiarity? The thing is that such a connection is formed not at the expense of the charged ions and their electrostatic attraction and not due to the difference in electronegativity and the presence of free electron pairs. That is, the ionic, metallic, covalent bonds have somewhat different nature and distinctive features of the particles being bound.

All metals are characterized by such characteristics as:

• A small number of electrons at the external energy level (except for some exceptions, in which they may be 6.7 and 8);
• Large atomic radius;
• Low ionization energy.

All this contributes to the easy separation of external unpaired electrons from the nucleus. There are a lot of free orbitals in the atom. The scheme for the formation of a metal bond will just show overlapping of numerous orbital cells of different atoms with each other, which as a result form a common intracrystalline space. Electrons from each atom are fed into it, which begin to wander freely around different parts of the lattice. Periodically, each of them joins the ion at the site of the crystal and turns it into an atom, then again detaches, forming an ion.

Thus, a metal bond is a bond between atoms, ions and free electrons in a general metal crystal. An electronic cloud that moves freely within a structure is called an "electron gas". They explain most of the physical properties of metals and their alloys.

How specifically does metal chemical bonding work? Examples can be given different. Let's try to look at a piece of lithium. Even if you take it the size of a pea, there will be thousands of atoms there. Let us imagine that each of these thousands of atoms gives its valence single electron into a common crystal space. At the same time, knowing the electronic structure of this element, you can see the number of empty orbitals. In lithium, there will be 3 (p-orbitals of the second energy level). Three for each atom of tens of thousands - this is the common space inside the crystal, in which the "electron gas" freely moves.

A substance with a metal bond is always strong. After all, the electron gas does not allow the crystal to crumble, but only displaces the layers and then restores them. It shines, has a certain density (most often high), fusibility, ductility and plasticity.

Where else is metal bonded? Examples of substances:

• Metals in the form of simple structures;
• All metal alloys with each other;
• All metals and their alloys in the liquid and solid state.

Specific examples can be given simply an incredible amount, because metals in the periodic system are more than 80!

Metal bond: the mechanism of education

If we consider it in its general form, we have already outlined the main points above. The presence of free atomic orbitals and electrons, which are easily detached from the nucleus due to the low ionization energy, are the main conditions for the formation of this type of connection. Thus, it turns out that it is realized between the following particles:

• Atoms in the lattice sites;
• Free electrons, which were valence metals;
• Ions at the sites of the crystal lattice.

As a result - a metal connection. The mechanism of education in general form is expressed by the following record: Me ⁰ - e ^- ↔ Me ^{n +} . From the diagram it is obvious which particles are present in the crystal of the metal.

Crystals themselves can have different shapes. It depends on the specific substance with which we are dealing.

Types of metal crystals

This structure of the metal or its alloy is characterized by very dense packing of particles. It is provided by ions at the crystal sites. The grids themselves can be of different geometric shapes in space.

1. The body-centered cubic lattice is alkali metals.
2. The hexagonal compact structure is all alkaline earth, except for barium.
3. The face-centered cubic is aluminum, copper, zinc, many transition metals.
4. The rhombohedral structure is in mercury.
5. Tetragonal - indium.

The heavier the metal and the lower it is in the periodic system, the more complex its packaging and the spatial organization of the crystal. In this case, the metallic chemical bond, examples of which can be given for each existing metal, is crucial for the construction of the crystal. Alloys have very diverse organizations in space, some of them have not yet been fully explored.

Communication characteristics: non-directivity

Covalent and metallic bonds have one very distinct distinctive feature. Unlike the first, the metal bond is not directional. What does it mean? That is, the electron cloud inside the crystal moves completely freely within its limits in different directions, each of the electrons is able to attach to absolutely any ion in the nodes of the structure. That is, interaction takes place in different directions. Hence they say that the metallic bond is non-directional.

The mechanism of covalent bond implies the formation of common electron pairs, that is, clouds of overlapping atoms. And it happens strictly on a certain line connecting their centers. Therefore, we are talking about the direction of such a connection.

Saturability

This characteristic reflects the ability of atoms to have limited or unrestricted interaction with others. Thus, the covalent and metallic bonds in this indicator are again opposites.

The first is saturable. The atoms taking part in its formation have a strictly defined number of valence external electrons, which take a direct part in the formation of the compound. More than he is, he will not have electrons. Therefore, the number of formed bonds is limited by valence. Hence the saturation of the bond. Due to this characteristic, most compounds have a constant chemical composition.

Metal and hydrogen bonds, on the contrary, are unsaturated. This is explained by the presence of numerous free electrons and orbitals inside the crystal. Also, the role is played by ions at the sites of the crystal lattice, each of which can become an atom and again an ion at any time.

Another characteristic of the metallic bond is the delocalization of the internal electron cloud. It manifests itself in the ability of a small number of common electrons to bind together many atomic nuclei of metals. That is, the density, as it were, is delocalized, distributed evenly among all the links of the crystal.

Examples of bond formation in metals

Let's consider some concrete variants which illustrate how a metallic bond is formed. Examples of substances are as follows:

• zinc;
• aluminum;
• potassium;
• chromium.

The formation of a metal bond between zinc atoms: Zn ⁰ - 2e ^- ↔ Zn ²⁺ . The zinc atom has four energy levels. Free orbitals, based on the electronic structure, he has 15 - 3 on the p-orbitals, 5 on 4 d and 7 on 4f. The electronic structure is as follows: 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ² 3d ¹⁰ 4p ⁰ 4d ⁰ 4f ⁰ , total in the atom is 30 electrons. That is, two free valence negative particles are able to move within 15 spacious and unoccupied orbitals. And so at each atom. As a result, there is a huge common space consisting of empty orbitals, and a small number of electrons linking the whole structure together.

Metal bond between aluminum atoms: AL ⁰ - e ^- ↔ AL ³⁺ . Thirteen electrons of an aluminum atom are located at three energy levels, which they clearly have enough of. Electronic structure: 1s ² 2s ² 2p ⁶ 3s ² 3p ¹ 3d ⁰ . Free orbitals - 7 pieces. Obviously, the electron cloud will be small in comparison with the general internal free space in the crystal.

Metal bond of chromium. This element is special in its electronic structure. After all, for the stabilization of the system there is a failure of an electron from 4s to 3d orbital: 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ¹ 3d ⁵ 4p ⁰ 4d ⁰ 4f ⁰ . A total of 24 electrons, of which six are obtained. It is they who go into the common electronic space for the formation of a chemical bond. Free orbitals 15, that is still much more than required for filling. Therefore, chromium is also a typical example of a metal with an appropriate bond in the molecule.

One of the most active metals, reacting even with ordinary water with ignition, is potassium. What explains these properties? Again, in many ways - a metallic type of connection. There are only 19 electrons in this element, but they are located at 4 energy levels. That is, on 30 orbitals of different sublevels. Electronic structure: 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ¹ 3d ⁰ 4p ⁰ 4d ⁰ 4f ⁰ . Only two valence electrons, with very low ionization energy. Free break away and go into the common electronic space. Orbital to move one atom 22 pieces, that is, a very large free space for "electronic gas."

Similarity and difference with other types of connections

In general, this issue has already been discussed above. One can only generalize and draw a conclusion. The main distinguishing features of all other types of communication features of metal crystals are:

• Several types of particles involved in the binding process (atoms, ions or atom-ions, electrons);
• Different spatial geometric structure of crystals.

With a hydrogen and ionic bond, metal combines unsaturation and non-directionality. With covalent polar - strong electrostatic attraction between particles. Separately with ionic - the type of particles in the nodes of the crystal lattice (ions). With covalent nonpolar - atoms in the nodes of the crystal.

Types of bonds in metals of different aggregate states

As we already noted above, the metal chemical bond, examples of which are given in the article, is formed in two aggregate states of metals and their alloys: solid and liquid.

The question arises: what type of bond is in the metal vapor? Answer: covalent polar and nonpolar. As in all compounds in the form of gas. That is, when the metal is heated for a long time and transferred from a solid state to a liquid bond, the crystal structure is preserved. However, when it comes to transferring a liquid to a vapor state, the crystal is destroyed and the metal bond is converted into a covalent one.