We are told a lot about hybrids. Both films and books tell about them, as well as science examines them. In the first two sources, hybrids are very dangerous creatures. They can bring too much evil. But hybridization is not always a bad thing. Quite often it is good.

An example of hybridization is everyone. We are all hybrids of two people - father and mother. So, the fusion of an egg and a sperm cell is also a kind of hybridization. It is this mechanism that allows evolution to move. In this case, hybridization with a negative sign also occurs. Let's look at this phenomenon as a whole.

Understanding hybridization

However, not only biology includes this concept... And let in the introduction an example was considered with hybrids as full-fledged individuals of an incomprehensible biological species. Moreover, this concept can be used in other sciences. And the meaning of this term will be slightly different. But at the same time, there is something in common. This is the word "union", which unites all possible meanings of this term.

Where does this concept exist?

The term "hybridization" is used in a number of sciences. And since most of the currently existing disciplines intersect, we can safely talk about the use of each meaning of this term in any science, one way or another related to natural research branches. Moreover, this term is most actively used in:

1. Biology. This is where the concept of a hybrid came from. Although, as always, when moving from science to daily life there was some distortion of the facts. We understand a hybrid as an individual resulting from the crossing of two other species. Although this is not always the case.
2. Chemistry. This concept means mixing several orbitals - a kind of paths for the movement of electrons.
3. Biochemistry. Here, the key concept is DNA hybridization.

As you can see, the third point is at the junction of two sciences. And this is absolutely normal practice. One and the same term can form a completely different meaning at the junction of two sciences. Let's take a closer look at the concept of hybridization in these sciences.

What is a hybrid?

A hybrid is a creature that is created through the process of hybridization. This concept refers to biology. Hybrids can be created either by accident or on purpose. In the first case, it can turn out to be animals that are created in the process of mating of two species of creatures.

For example, they talk about the appearance in cats and dogs of children who are not one of them. Sometimes hybrids are created on purpose. For example, when a cherry is attached to an apricot, we are dealing with just a special hybridization.

Hybridization in biology

Biology - interesting science... And the concept of hybridization in it is no less fascinating. This term means the union of the genetic material of different cells in one. These can be representatives of one species, or several. Accordingly, there is a division into such hybridization varieties.

• Intraspecific hybridization. This is when two individuals of the same species create a descendant. Human can be considered an example of intraspecific hybridization. It turned out in the process of fusion of germ cells of representatives of one biological species.
• Interspecies hybridization. This is when similar, but belonging to different species, animals are interbred. For example, a hybrid of a horse and a zebra.
• Remote hybridization. This is when representatives of even one species interbreed, but at the same time they are not united by family ties.

Each of these varieties helps more than just evolution. Scientists are also actively trying to breed different types Living creatures. Works best with plants. There are several reasons for this:

• Different number of chromosomes. Each species has not only a specific number of chromosomes, but also their set. All this interferes with the reproduction of offspring.
• Only hybrid plants can reproduce. And that is not always the case.
• Only plants can be polyploid. For a plant to reproduce, it must become polyploid. In the case of animals, this is certain death.
• Possibility of vegetative hybridization. It is very simple and convenient way creating hybrids of several plants.

These are the reasons why crossing two plants is much easier and more effective. In the case of animals, it may be possible in the future to achieve the possibility of reproduction. But at the moment, the opinion is considered official in biology that hybrid animals lose their ability to reproduce, since these individuals are genetically unstable. Therefore, it is not known what their reproduction can lead to.

Types of hybridization in biology

Biology is a fairly broad science in its specialization. There are two types of hybridization, which it provides:

1. Genetic. This is when one of two cells is made with a unique set of chromosomes.
2. Biochemical. An example of this type is DNA hybridization. This is when complementary nucleic acids are combined into one DNA.

Can be divided into large quantity varieties. But we did this in the previous subsection. Thus, distant and intraspecific hybridization are components of the first type. And there the classification expands even more.

Vegetative hybridization concept

Vegetative hybridization is a concept in biology that means a type of crossing of two plants in which part of one species takes root on the other. That is, hybridization occurs by combining two different parts organism. Yes, that is how a plant can be characterized. After all, he also has his own organs, united into a whole system. Therefore, if you call a plant an organism, there is nothing wrong with that.

Vegetative hybridization has several advantages. It:

• Convenience.
• Simplicity.
• Efficiency.
• Practicality.

These advantages make this type of crossing very popular with gardeners. There is also such a thing as somatic hybridization. This is when not sex cells are crossed, but somatic cells, or rather, their protoplasts. This method crossing is carried out when it is impossible to create a hybrid by standard sexual intercourse between several plants.

Hybridization in chemistry

But now we will step back a little from biology and talk about another science. Chemistry has its own concept, it is called "hybridization of atomic orbitals". This is a very complex term, but if you understand a little about chemistry, then there is nothing complicated about it. First you need to explain what an orbital is.

This is a kind of path along which the electron moves. We were taught this at school. And if it happens that the orbital data different types mix, you get a hybrid. There are three kinds of phenomenon called orbital hybridization. These are the following varieties:

• sp-hybridization - one s and another p orbital;
• sp 2 -hybridization - one s and two p orbitals;
• sp 3 -hybridization - one s and three p orbitals are connected.

This topic is difficult enough to study, and it should be considered inseparably from the rest of the theory. Moreover, the concept of hybridization of orbitals concerns more the end of this topic, and not the beginning. After all, you need to study the very concept of orbitals, what they are, and so on.

conclusions

So, we figured out the meanings of the concept of "hybridization". This turns out to be quite interesting. For many, it was a discovery that chemistry also has this concept. But if such people did not know this, then what could they learn? And so, there is development. It is important not to stop training your erudition, as this will definitely characterize you from the good side.

Hybridizationcalled a hypothetical mixing process different types, but close in energy orbitals of a given atom with the appearance of the same number of new (hybrid 1) orbitals, identical in energy and shape.

Hybridization of atomic orbitals occurs during the formation of covalent bonds.

Hybrid orbitals have the shape of a three-dimensional asymmetric figure eight, strongly elongated to one side from the atomic nucleus:.

This shape causes a stronger overlap of hybrid orbitals with orbitals (pure or hybrid) of other atoms than in the case of pure atomic orbitals and leads to the formation of stronger covalent bonds. Therefore, the energy spent on the hybridization of atomic orbitals is more than compensated for by the release of energy due to the formation of stronger covalent bonds with the participation of hybrid orbitals. The name of the hybrid orbitals and the type of hybridization are determined by the number and type of atomic orbitals involved in hybridization, for example: sp-, sp 2 -, sp 3 -, sp 2 d- orsp 3 d 2 -hybridization.

The directionality of the hybrid orbitals, and hence the geometry of the molecule, depend on the type of hybridization. In practice, the inverse problem is usually solved: first, the geometry of the molecule is established experimentally, after which the type and shape of the hybrid orbitals involved in its formation are described.

sp -Hybridization. Two hybrid sp- as a result of mutual repulsion, the orbitals are located relative to the atomic nucleus in such a way that the angle between them is 180 ° (Fig. 7).

Rice. 7. Mutual arrangement in space of two sp- hybrid orbitals of one atom: a - surfaces covering areas of space where the probability of an electron being present is 90%; b - conditional image.

As a result of this arrangement of hybrid orbitals, molecules of the composition AX 2, where A is the central atom, have linear structure, that is, the covalent bonds of all three atoms are located on one straight line. For example, in a state sp- hybridization are the valence orbitals of the beryllium atom in the BeCl 2 molecule (Fig. 8). Linear configuration due to sp- Hybridizations of valence orbitals of atoms are also observed in BeH 2, Be (CH 3) 2, ZnCl 2, CO 2, HC≡N and a number of others.

Rice. 8. Three-atom linear molecule of beryllium chloride BeCl 2 (in the gaseous state): 1 - 3R- Cl atom orbital; 2 - two sp- hybrid orbitals of the Be atom.

s R 2 -Hybridization. Consider the hybridization of one s- and two R- orbitals. In this case, as a result of a linear combination of three orbitals, three hybrid sR 2 -orbital. They are located in the same plane at an angle of 120 ° to each other (Fig. 9). sR 2 -Hybridization is characteristic of many boron compounds, which, as shown above, in an excited state has three unpaired electrons: one s- and two R-electron. Overlapping sR 2 -orbitals of the boron atom with the orbitals of other atoms, three covalent bonds are formed, equivalent in length and energy. Molecules in which the valence orbitals of the central atom are in the state sR 2 -hybridization, have a triangular configuration. The angles between the covalent bonds are 120 °. Capable of sR 2 -hybridization are the valence orbitals of boron atoms in BF 3, BC1 3 molecules, carbon and nitrogen atoms in CO 3 2 -, NO 3 - anions.

Rice. 9. Mutual arrangement in space of three sR 2 -hybrid orbitals.

s R 3 -Hybridization. Substances are very widespread in the molecules of which the central atom contains four sR 3 -orbitals formed as a result of a linear combination of one s- and three R-orbitals. These orbitals are located at an angle of 109˚28 ′ to each other and directed to the vertices of the tetrahedron, in the center of which there is an atomic nucleus (Fig. 10 a).

Formation of four equivalent covalent bonds due to overlapping sR 3 -orbitals with orbitals of other atoms is characteristic of carbon atoms and other elements of the IVA group; this determines the tetrahedral structure of molecules (CH 4, CC1 4, SiH 4, SiF 4, GeH 4, GeBr 4, etc.).

Rice. 10. Influence of non-bonding electron pairs on the geometry of molecules:

a- methane (no non-binding electron pairs);

b- ammonia (one non-binding electron pair);

v- water (two non-binding pairs).

Lonely electron pairs hybrid orbit lei . In all the examples considered, the hybrid orbitals were "populated" by single electrons. However, it is not uncommon for a hybrid orbital to be "populated" by an electron pair. This affects the geometry of the molecules. Since the non-bonding electron pair is affected by the nucleus of only its own atom, and the bonding electron pair is under the influence of two atomic nuclei, the non-bonding electron pair is closer to atomic nucleus than binding. As a result, the non-bonding electron pair repels the bonding electron pairs more strongly than they repel each other. Graphically, for clarity, the large repulsive force acting between the non-bonding and bonding electron pairs can be depicted as a larger electron orbital of the non-bonding pair. A non-binding electron pair exists, for example, at the nitrogen atom in the ammonia molecule (Fig. 10 b). As a result of interaction with bonding electron pairs, the H-N-H bond angles are reduced to 107.78 ° compared to 109.5 ° typical for a regular tetrahedron.

An even greater repulsion is experienced by bonding electron pairs in a water molecule, where the oxygen atom has two non-bonding electron pairs. As a result, the bond angle H-O-H in the water molecule is 104.5 ° (Fig. 10 v).

If a non-bonding electron pair, as a result of the formation of a covalent bond by the donor-acceptor mechanism, turns into a bonding one, then the repulsive forces between this bond and other covalent bonds in the molecule equalize; the angles between these bonds are also aligned. This happens, for example, with the formation of an ammonium cation:

Participation in hybridization d -orbitals. If the energy of atomic d- orbitals is not very different from energies s- and R- orbitals, then they can participate in hybridization. The most common type of hybridization involving d- orbitals is sR 3 d 2 - hybridization, which results in the formation of six hybrid orbitals equivalent in shape and energy (Fig. 11 a), located at an angle of 90˚ to each other and directed to the vertices of the octahedron, in the center of which there is an atomic nucleus. Octahedron (Fig. 11 b) – is a regular octahedron: all edges in it are of equal length, all faces are regular triangles.

Rice. eleven. sR 3 d 2 - Hybridization

Less common sR 3 d- hybridization with the formation of five hybrid orbitals (Fig. 12 a) directed to the vertices of the trigonal bipyramid (Fig. 12 b). The trigonal bipyramid is formed by the joining of two isosceles pyramids common ground- regular triangle. Bold strokes in Fig. 12 b edges of equal length are shown. Geometrically and energetically sR 3 d- hybrid orbitals are unequal: three "equatorial" orbitals are directed to the vertices of a regular triangle, and two "axial" - up and down perpendicular to the plane of this triangle (Fig. 12 v). The angles between the "equatorial" orbitals are equal to 120 °, as for sR 2 - hybridization. The angle between the "axial" and any of the "equatorial" orbitals is 90 °. Accordingly, the covalent bonds that are formed with the participation of "equatorial" orbitals differ in length and energy from the bonds in the formation of which the "axial" orbitals are involved. For example, in the PC1 5 molecule, the “axial” bonds are 214 pm long, and the “equatorial” ones are 202 pm long.

Rice. 12. sR 3 d- Hybridization

Thus, considering covalent bonds as a result of overlapping atomic orbitals, it is possible to explain the geometry of the resulting molecules and ions, which depends on the number and type of atomic orbitals involved in the formation of bonds. The concept of hybridization of atomic orbitals, it is necessary to understand that hybridization is a conditional technique that allows you to visually explain the geometry of a molecule through a combination of AOs.

Atomic orbital hybridization is a process that allows you to understand how atoms modify their orbitals to form compounds. So what is hybridization and what types are there?

General characteristics of hybridization of atomic orbitals

Hybridization of atomic orbitals is a process in which different orbitals of the central atom are mixed, resulting in the formation of orbitals of the same characteristics.

Hybridization occurs during the formation of a covalent bond.

The hybrid orbital has a head start with the sign of infinity or an asymmetric inverted figure eight, elongated to the side of the atomic nucleus. This shape causes a stronger overlap of hybrid orbitals with orbitals (pure or hybrid) of other atoms than in the case of pure atomic orbitals and leads to the formation of stronger covalent bonds.

Rice. 1. Hybrid orbital appearance.

For the first time the idea of ​​hybridization of atomic orbitals was put forward by the American scientist L. Pauling. He believed that the atom entering into a chemical bond has different atomic orbitals (s-, p-, d-, f-orbitals), then the result is hybridization of these orbitals. The essence of the process is that equivalent atomic orbitals are formed from different orbitals.

Types of hybridization of atomic orbitals

There are several types of hybridization:

• ... This kind of hybridization occurs when one s-orbital and one p-orbital are mixed. As a result, two full-fledged sp orbitals are formed. These orbitals are located to the atomic nucleus in such a way that the angle between them is 180 degrees.

Rice. 2. sp-hybridization.

• sp2 hybridization... This kind of hybridization occurs when one s orbital and two p orbitals are mixed. The result is the formation of three hybrid orbitals, which are located in the same plane at an angle of 120 degrees to each other.
• ... This kind of hybridization occurs when one s orbital and three p orbitals are mixed. As a result, four full-fledged sp3 orbitals are formed. These orbitals are directed towards the apex of the tetrahedron and are located at an angle of 109.28 degrees to each other.

sp3 hybridization is typical for many elements, for example, the carbon atom and other substances of IVA group (CH 4, SiH 4, SiF 4, GeH 4, etc.)

Rice. 3. sp3 hybridization.

More complex types of hybridization with the participation of atomic d-orbitals are also possible.

What have we learned?

Hybridization is a complex chemical process where different orbitals of an atom form the same (equivalent) hybrid orbitals. The first to voice the theory of hybridization was the American L. Pauling. There are three main types of hybridization: sp-hybridization, sp2-hybridization, sp3-hybridization. There are also more complex types of hybridization in which d-orbitals are involved.

Hybridization concept

Hybridization concept of valence atomic orbitals was proposed by the American chemist Linus Pauling to answer the question why, when the central atom has different (s, p, d) valence orbitals, the bonds formed by it in polyatomic molecules with the same ligands are equivalent in their energy and spatial characteristics.

The concept of hybridization is central to the valence bond method. Hybridization itself is not a real physical process, but only convenient model, which makes it possible to explain the electronic structure of molecules, in particular, hypothetical modifications of atomic orbitals during the formation of a covalent chemical bond, in particular, the alignment of the lengths of chemical bonds and bond angles in a molecule.

The concept of hybridization was successfully applied to the qualitative description of simple molecules, but was later extended to more complex ones. Unlike the theory of molecular orbitals, it is not strictly quantitative, for example, it is not able to predict the photoelectron spectra of even such simple molecules as water. It is currently used mainly for methodological purposes and in synthetic organic chemistry.

This principle is reflected in the theory of repulsion of electron pairs Gillespie - Nyholm. First and most important rule which was formulated as follows:

The second rule is that "All electron pairs included in the valence electron shell are considered to be located at the same distance from the nucleus".

Types of hybridization

sp hybridization

Occurs when one s- and one p-orbitals are mixed. Two equivalent sp-atomic orbitals are formed, located linearly at an angle of 180 degrees and directed in different directions from the nucleus of the carbon atom. The two remaining non-hybrid p-orbitals are located in mutually perpendicular planes and participate in the formation of π-bonds, or are occupied with lone pairs of electrons.

sp 2 -hybridization

Occurs when one s and two p orbitals are mixed. Three hybrid orbitals are formed with axes located in the same plane and directed to the vertices of the triangle at an angle of 120 degrees. The non-hybrid p-atomic orbital is perpendicular to the plane and, as a rule, participates in the formation of π-bonds

sp 3 -hybridization

It occurs when one s- and three p-orbitals are mixed, forming four sp3-hybrid orbitals of equal shape and energy. They can form four σ-bonds with other atoms or be filled with lone pairs of electrons.

The axes of sp3-hybrid orbitals are directed towards the vertices of a regular tetrahedron. The tetrahedral angle between them is 109 ° 28 ", which corresponds to the lowest electron repulsion energy. Also, sp3-orbitals can form four σ-bonds with other atoms or be filled with lone pairs of electrons.

Hybridization and molecular geometry

The concept of hybridization of atomic orbitals underlies the theory of repulsion of electron pairs Gillespie-Nicholm. Each type of hybridization corresponds to a strictly defined spatial orientation of the hybrid orbitals of the central atom, which allows it to be used as the basis of stereochemical representations in non organic chemistry.

The table shows examples of the correspondence between the most common types of hybridization and the geometric structure of molecules on the assumption that all hybrid orbitals are involved in the formation chemical bonds(there are no lone electron pairs).

Hybridization type	Number hybrid orbitals	Geometry	Structure	Examples of
sp	2	Linear		BeF 2, CO 2, NO 2 +
sp 2	3	Triangular		BF 3, NO 3 -, CO 3 2-
sp 3	4	Tetrahedral		CH 4, ClO 4 -, SO 4 2-, NH 4 +
dsp 2	4	Square		Ni (CO) 4, XeF 4
sp 3 d	5	Hexahedral		PCl 5, AsF 5
sp 3 d 2	6	Octahedral		SF 6, Fe (CN) 6 3-, CoF 6 3-

Links

Literature

• Pauling L. The nature of the chemical bond / Per. from English M. E. Dyatkina. Ed. prof. Ya.K. Syrkin. - M .; L .: Goskhimizdat, 1947 .-- 440 p.
• Pauling L. general chemistry... Per. from English - M .: Mir, 1974 .-- 846 p.
• Minkin V.I., Simkin B. Ya., Minyaev R.M. The theory of the structure of molecules. - Rostov-on-Don: Phoenix, 1997 .-- S. 397-406. - ISBN 5-222-00106-7
• Gillespie R. Geometry of molecules / Per. from English E.Z.Zasorin and V.S.Mastryukov, ed. Yu.A. Pentina. - M .: Mir, 1975 .-- 278 p.

see also

Notes (edit)

Wikimedia Foundation. 2010.

A polyatomic molecule with the appearance of identical orbitals, equivalent in their characteristics.

Collegiate YouTube

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Hybridization of electron orbitals

Cytology. Lecture 46. Orbital hybridization

Sp3 hybrid orbitals

Subtitles

Hybridization concept

Hybridization concept of valence atomic orbitals was proposed by the American chemist Linus Pauling to answer the question why, when the central atom has different (s, p, d) valence orbitals, the bonds formed by it in polyatomic molecules with the same ligands are equivalent in their energy and spatial characteristics.

The concept of hybridization is central to the valence bond method. Hybridization itself is not a real physical process, but only a convenient model that makes it possible to explain the electronic structure of molecules, in particular, hypothetical modifications of atomic orbitals during the formation of a covalent chemical bond, in particular, the alignment of chemical bond lengths and bond angles in a molecule.

The concept of hybridization was successfully applied to the qualitative description of simple molecules, but was later extended to more complex ones. Unlike the theory of molecular orbitals, it is not strictly quantitative, for example, it is not able to predict the photoelectron spectra of even such simple molecules as water. It is currently used mainly for methodological purposes and in synthetic organic chemistry.

This principle is reflected in the theory of repulsion of electron pairs Gillespie - Nyholm, the first and most important rule, which was formulated as follows:

The second rule was that "All electron pairs included in the valence electron shell are considered to be located at the same distance from the nucleus".

Types of hybridization

sp-hybridization

Occurs when one s- and one p-orbitals are mixed. Two equivalent sp-atomic orbitals are formed, located linearly at an angle of 180 degrees and directed in different directions from the nucleus of the central atom. The two remaining non-hybrid p-orbitals are located in mutually perpendicular planes and participate in the formation of π-bonds, or are occupied by unshared electron pairs.

sp 2 -Hybridization

Occurs when one s and two p orbitals are mixed. Three hybrid orbitals are formed with axes located in the same plane and directed to the vertices of the triangle at an angle of 120 degrees. The non-hybrid p-atomic orbital is perpendicular to the plane and, as a rule, participates in the formation of π-bonds

sp 3 -Hybridization

It occurs when one s- and three p-orbitals are mixed, forming four sp 3 -hybrid orbitals equivalent in shape and energy. They can form four σ-bonds with other atoms or be filled with lone pairs of electrons.

The axes of the sp 3 -hybrid orbitals are directed to the vertices of the tetrahedron, while the nucleus of the central atom is located in the center of the described sphere of this tetrahedron. The angle between any two axes is approximately 109 ° 28 ", which corresponds to the lowest electron repulsion energy. Also sp 3 -orbitals can form four σ-bonds with other atoms or be filled with lone pairs of electrons. This state is typical for carbon atoms in saturated hydrocarbons and, accordingly in alkyl radicals and their derivatives.

Hybridization and molecular geometry

The concept of hybridization of atomic orbitals underlies the theory of repulsion of electron pairs Gillespie-Nyholm. Each type of hybridization corresponds to a strictly defined spatial orientation of the hybrid orbitals of the central atom, which allows it to be used as the basis for stereochemical concepts in inorganic chemistry.

The table shows examples of the correspondence between the most common types of hybridization and the geometric structure of molecules on the assumption that all hybrid orbitals are involved in the formation of chemical bonds (there are no lone electron pairs).