All currently known chemical elements, arranged in the periodic table, conventionally divided into two groups: metals and non-metals.In order to become not only elements and compounds, chemicals may interact with each other, they should exist in the form of simple and complex compounds.
This is why some electrons are trying to take, and others - to give.Replenishing each other so as to form elements of different chemical molecules.But what allows them to be held together?Why is there such a matter of strength, which is not subject to destroy even the most serious tool?Others, on the contrary, are destroyed by the slightest exposure.All this is due to the formation of various types of chemical bonds between atoms in the molecule, the formation of a specific lattice structure.
Types of chemical bonds in compounds
Total possible to allocate 4 basic types of chemical bonds.
- covalent nonpolar.Formed between two identical non-metals by sharing of electrons, forming common electron pairs.In education, it is attended unpaired valence particles.Examples of halogens, oxygen, hydrogen, nitrogen, sulfur, phosphorus.
- polar covalent.Formed between two different non-metals or between very weak on the properties of the metal and nonmetal weak in electronegativity.At the heart are also common electron pairs and pulling them to her the atom, the electron affinity is higher.Examples: NH3, SiC, P2O5 and others.
- hydrogen bond.The most unstable and weak, is formed between the highly electronegative atom of one molecule and the other positive.This occurs most often when dissolved substances in water (alcohols, ammonia and so on).Through such connection may exist macromolecule proteins, nucleic acids, complex carbohydrates, and so forth.
- ionic bond.Formed due to electrostatic attraction forces raznozaryazhennyh ions of metal and nonmetal.The greater the difference in this indicator, the more pronounced is the ionic nature of the interaction.Exemplary compounds: binary salt, complex compound - alkali.
- metallic bond, the mechanism of formation which, as well as properties that will be discussed further.Formed in metals, 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 bond benchmark.They're just the unit symbol.After all, the basis of all interactions is a single principle - elektronnostaticheskoe interaction.Therefore, ionic, metallic, covalent bonding and hydrogen have a single chemical nature and are only borderline cases to 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 considerable part of them has been received by man by nuclear reactions in the laboratory, they are radioactive with short half-life.
However, the majority - are natural elements that form the whole rocks and ores, are part of the most important compounds.It is because of these people have learned to cast alloys, and make a lot of beautiful and important products.This is such as copper, iron, aluminum, silver, gold, chrome, manganese, nickel, zinc, lead and others.
for all metals are some common physical characteristics, which explains the scheme of formation of metallic bonds.What are these characteristics?
- malleability and ductility.It is known that many metals can be rolled down even to the point of foil (gold, aluminum).Among other prepared wire, flexible sheets of metal, products that can be deformed by a physical impact, but then recover form after its termination.These are the qualities of metals and called malleability and ductility.The reason for this feature - a metallic type of bond.The ions and electrons in the crystal slide relative to each other without breaking, which allows to preserve the integrity of the entire structure.
- metallic luster.It also explains the metallic bond, the mechanism of formation, its characteristics and features.Thus, not all particles are able to absorb or reflect light waves of the same length.The atoms of most metals reflect short-wave rays and become almost the same silver color, white, pale bluish.Exceptions are copper and gold, their color is brown-red and yellow, respectively.They are able to reflect a more long-wave radiation.
- thermal and electrical conductivity.These properties are also explained by the structure of the crystal lattice, and the fact that in its formation realized metallic type of bond.Due to the "electron gas", moving inside the crystal, electricity and heat instantly and evenly distributed between all the atoms and ions and conducted through the metal.
- solid state under normal conditions.Here, the only exception is mercury.All other metals - is certainly strong, solid compounds, as well as their alloys.It is also the result of the metals present in the metal bond.The mechanism of formation of this type of binding the particles fully confirms properties.
It is the basic physical characteristics of metals, which explains exactly defines formation of the metallic bond scheme.A relevant way to connect it to the atoms of elements of metals and their alloys.That is for them in the solid and liquid states.
metal type of chemical bond
What are its features?The fact is that such a relationship is formed not by raznozaryazhennyh ions and electrostatic attraction and not due to the difference in electronegativity and availability of electron pairs.That is ionic, metallic, covalent bond have several different nature and distinctive features of linking particles.
all metals are inherent characteristics such as:
- small number of electrons in the outer energy level (except for certain exceptions, for which there can be 6,7 and 8);
- large atomic radius;
- low ionization energy.
All this contributes to easy separation of the outer unpaired electrons from the nucleus.This free orbitals of the atom remains very much.Scheme of the metallic bond is just and will show the overlap of many different cells orbiting atoms together, and that as a result of the general form intracrystalline space.It serves the electrons from each atom, which are beginning to wander freely in different parts of the grid.Periodically, each of which is joined to an ion in the crystal unit and converts it into an atom then detached, forming ion.
Thus, the metallic bond - a bond between atoms, ions and free electrons in the overall crystal metal.The electron cloud, move freely inside the structure, called the "electron gas".It is explained to them most of the physical properties of metals and their alloys.
How specifically implements a metallic chemical bond?Examples include different.Let's try to see on a piece of lithium.Even if we take his pea-sized, there will be thousands of atoms.So imagine that each of these thousands of atoms gives a valence electron in a single common crystal space.At the same time, knowing the electronic structure of the element, you can see the number of vacant orbitals.Lithium will have their 3 (p-orbital of the second energy level).Three in every atom of the tens of thousands - this is a common space within the crystal, in which the "electron gas" moves freely.
substance with a metal bond is always strong.After the electron gas does not allow crystal to fall, but only shifts the layers and then recovers.It is shiny, has a certain density (usually high), fusibility, malleability and ductility.
Where else realized metallic bond?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 are just incredible amount, as metals in the periodic system of more than 80!
metallic bond: formation mechanism
If you consider it in general terms, the main points we have outlined above.Availability of atomic orbitals and electrons easily detached from the core due to the low ionization energy - these are the main conditions for the formation of this type of communication.Thus, it turns out that it is implemented between the following particles:
- atoms in the lattice sites;
- free electrons that were in the metal valence;
- ions in the crystal lattice sites.
The result - a metallic bond.The mechanism of formation generally expressed by the following entry: Me0 - e- ↔ Men. +From the diagram evidently, any particles present in the metal crystal.
crystals themselves may have different shapes.It depends on the material with which we are dealing.
types of crystals
This metal structure of the metal or alloy is characterized by a very dense packing of particles.It provides the ions in the crystal sites.By themselves, the lattice can be of different geometric shapes in space.
- Obemnotsentricheskaya cubic lattice - alkali metals.
- hexagonal compact structure - all alkaline, except for barium.
- Granetsentricheskaya cubic - aluminum, copper, zinc, many transition metals.
- rhombohedral structure - from mercury.
- tetragonal - indium.
The heavy metals and the lower it is in the periodic table, the harder it is packaging and spatial organization of the crystal.This metallic chemical bond, examples of which can be reduced for each existing metal is decisive in the construction of the crystal.The alloys have a very diverse organization in space, some of them are still not yet fully understood.
Communication Specifications:
not directed covalent and metallic bond has a very pronounced distinctive feature.Unlike the first, the metallic bond is not directed.What does it mean?That is, the electron cloud within the crystal moves quite freely within it in different directions, each of the electron is able to join perfectly any ion in the nodes of the structure.That is, the interaction is carried out in different directions.Hence, they say that the metallic bond - non-directional.
mechanism involves the formation of a covalent bond shared electron pairs, ie clouds of atoms overlap.And it occurs strictly on a certain line connecting their centers.So talk about the direction of such a connection.
saturation
This characteristic reflects the ability of atoms to a limited or unlimited interaction with others.For example, covalent and metallic bond on this indicator again are opposites.
first is saturated.The atoms involved in its formation, have a fixed number of valence electrons outside, directly involved in the formation of compounds.More than eating, it will not be the electrons.Therefore, the number of bonds formed limited valence.Hence saturation connection.Due to this characteristic, most of the compounds have a constant chemical composition.
metal and hydrogen bonds, on the other hand, non-saturating.This is due to the presence of numerous free electrons within the crystal orbitals.Also play a role in the ion lattice sites, each of which may be ion atom and again at any time.
Another characteristic of the metallic bond - delocalization internal electron cloud.It is manifested in the ability of a small number of electrons shared between a set of binding atomic nuclei metals.That is, the density of delocalized as it is distributed equally among all units of the crystal.
Examples of bonding in metals
consider several specific options which illustrate how the metallic bond is formed.Examples of substances following:
- zinc;
- aluminum;
- potassium;
- chrome.
formation of metallic bonds between atoms of zinc: Zn0 - 2e- ↔ Zn2 +.Zinc atom has four power levels.Free orbitals on the basis of the electronic structure, it has 15 - 3 p-orbitals, 5 to 4 d, and 7 4f.Electronic structure of the following: 1s22s22p63s23p64s23d104p04d04f0, just in the atom 30 electrons.That is, two free valence negative particles are able to move in the range of 15 spacious and nobody occupied orbitals.And since each atom.The result - a huge total space of the empty orbitals, and a small number of electrons that bind the whole structure together.
metallic bond between the atoms of aluminum: AL0 - e- ↔ AL3 +.Thirteen of the electrons of an atom of aluminum placed on three energy levels, which they obviously lack abundance.Electronic structure: 1s22s22p63s23p13d0.Free orbitals - 7 pieces.Obviously, the electron cloud will be small compared with the total internal free space in the crystal.
chrome metallic bond.This item is special in its electronic structure.After all, to stabilize the system is the failure of an electron from 4s to 3d orbital: 1s22s22p63s23p64s13d54p04d04f0.Only 24 of the electron from the valence which turns six.They go into a common electronic space on the formation of chemical bonds.Free orbitals 15, that is still much more than is required for filling.Therefore, chromium - as a typical example of the metal to the corresponding bond in the molecule.
One of the most active metals that react even with normal water of ignition is potassium.What accounts for such properties?Again, in many respects - a metallic type of bond.Electrons this item only 19, but they are located as much as 4 power levels.That is 30 different orbitals sublevels.Electronic structure: 1s22s22p63s23p64s13d04p04d04f0.Just two valence electrons, with a very low ionization energy.Available break away and go to the common electronic space.Orbitals to move one atom of 22 pieces, that is a very broad space for the "electron gas".
similarities and differences with other types of bonds
In general, the issue has already been discussed above.We can only summarize and conclude.The main distinctive from all other types of communication features is the metal crystals are:
- several types of particles participating in the process of binding (atoms, ions or atoms, ions, electrons);
- different spatial geometric structure of crystals.
with hydrogen and ionic metal combines satiation and undirected.With polar covalent - strong electrostatic attraction between the particles.Separately, ion-- type particles in the crystalline lattice points (ions).With covalent nonpolar - atoms in the crystal sites.
Types of bonds in the aggregate state of metal of different
As we noted above, the metallic chemical bond, exemplified in an article produced in the two states of aggregation metals and their alloys: solid and liquid.
The question is: what type of connection in metal vapors?Answer: covalent polar and nonpolar.As with all compounds present in a gas.That is, the prolonged heating of the metal and its transfer from the solid to the liquid state due not torn, and the crystal structure is maintained.However, when it comes to transfer the liquid to the vapor state, the crystal is destroyed and converted into a metallic bond covalent.
