Instructions
Consider the molecule of the simplest saturated hydrocarbon, methane. Its looks like this: CH4. The spatial model of a molecule is a tetrahedron. The carbon atom forms bonds with four hydrogen atoms that are absolutely identical in length and bond energy. In them, according to the above example, 3 - P electron and 1 S - electron participate, the orbital of which began to exactly correspond to the orbitals of the other three electrons as a result of what happened. This type of hybridization is called sp ^ 3 hybridization. It is inherent in all the ultimate.
But the simplest representative of unsaturated ones is ethylene. Its formula is as follows: C2H4. What type of hybridization is inherent in the carbon in the molecule of this substance? As a result, three orbitals are formed in the form of asymmetric "eights" lying in one plane at an angle of 120 ^ 0 to each other. They were formed by 1 - S and 2 - P electrons. The last 3rd P - the electron did not change its orbital, that is, it remained in the form of the correct "eight". This type of hybridization is called sp ^ 2 hybridization.
How are bonds formed in a molecule? Two hybridized orbitals of each atom entered with two hydrogen atoms. The third hybridized orbital formed a link with the same orbital of the other. Are the remaining P orbitals? They are "attracted" to each other on both sides of the plane of the molecule. A bond has formed between the carbon atoms. It is atoms with a "double" bond that sp ^ 2 is inherent in.
And what happens in the acetylene molecule or? Its formula is as follows: C2H2. In each carbon atom, only two electrons undergo hybridization: 1 - S and 1 - P. The other two retained their orbitals in the form of "regular eights" overlapping "in the plane of the molecule and on either side of it. That is why this type of hybridization is called sp - hybridization. It is inherent in atoms with a triple bond.
Everything the words existing in a particular language can be divided into several groups. This is important when defining both meaning and grammatical functions. the words... Referring it to a certain type, you can modify it according to the rules, even if you haven't met it before. Element types the words lexicology deals with the composition of the language.
You will need
- - text;
- - dictionary.
Instructions
Select the word you want to define the type of. Its belonging to one or another part of speech does not yet play a role, as well as its form and function in a sentence. It can be absolutely any word. If it is not indicated in the assignment, write down the first one that comes across. Determine if it is naming an object, quality, action or not. For this parameter, all the words are divided into significant, pronominal, numerals, service and interjection. To the first type include nouns, adjectives, verbs, etc. They designate the names of objects, qualities and actions. The second type of words that have a naming function is the pronominal. The ability to name is absent in the interjection and service types. These are relatively small groups of words, but they are in everyone.
Determine if a given word is capable of expressing a concept. This function is available for the words units of a significant type, because it is they that form the conceptual series of any language. However, any number also belongs to the category of concepts, and, accordingly, also carries this function. Official words also have it, but pronouns and interjections do not.
Consider how the word will be if it appears in a sentence. Can it be? It can be any word of a significant type. But this opportunity is there for, as well as for the numeral. But the service the words play an auxiliary role, neither the subject, nor, nor the secondary members of the sentence, they can not be, as well as interjections.
For convenience, you can create a plate of four columns of six rows. On the top row, name the appropriate columns for Word Types, Title, Concept, and Can I Be a Sentence Member. In the first left column, write down the names of the types of words, there are five of them. Determine which functions a given word has and which it does not. Put pluses and in the appropriate boxes. If all three columns have pluses, then this is a significant type. The pronominal will have pluses in the first and third columns, in the second and third. Service the words can only express the concept, that is, they have one plus in the second column. Opposite interjections in all three columns will be minuses.
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Hybridization is the process of obtaining hybrids - plants or animals, derived from the crossing of different varieties and breeds. The word hybrid (hibrida) from the Latin language is translated as "cross".
Hybridization: natural and artificial
The hybridization process is based on combining the genetic material of different cells from different individuals in one cell. Distinguishes between intraspecific and distant, in which the connection of different genomes occurs. In nature, natural hybridization has taken place and continues to occur without human participation all the time. It was by crossing within a species that plants changed and improved and new varieties and breeds of animals appeared. From the point of view, there is a hybridization of DNA, nucleic acids, changes at the atomic and intra-atomic levels.
In academic chemistry, hybridization is understood as a specific interaction in the molecules of matter of atomic orbitals. But this is not a real physical process, but only a hypothetical model, a concept.
Hybrids in crop production
In 1694, the German scientist R. Camerius proposed to artificially receive. And in 1717, English T. Fairchidl crossed different types of carnations for the first time. Today, intraspecific hybridization of plants is carried out in order to obtain high-yielding or adapted, for example, frost-resistant varieties. Hybridization of forms and varieties is one of the methods of plant breeding. Thus, a huge number of modern varieties of agricultural crops have been created.
With distant hybridization, when representatives of different species are crossed and different genomes are combined, the resulting hybrids in most cases do not give offspring or produce hybrids of poor quality. That is why there is no point in leaving the seeds of the hybrid cucumbers ripe in the garden, and every time buying their seeds in a specialized store.
Animal breeding
In the world, natural hybridization, both intraspecific and distant, also takes place. Mules were known to man as far back as two thousand years BC. And now the mule and hinny are used in the household as a relatively cheap working animal. True, such hybridization is interspecific, therefore male hybrids are born necessarily sterile. Females, on the other hand, can very rarely give offspring.
A mule is a hybrid of a mare and a donkey. A hybrid obtained from crossing a stallion and a donkey is called a hinny. Mules are specially bred. They are taller and stronger than a hinnie.
But crossing a domestic dog with a wolf was a very common activity among hunters. Then, the resulting offspring was subjected to further selection, as a result, new breeds of dogs were created. Today, animal breeding is an important component of the success of the livestock industry. Hybridization is carried out purposefully, with a focus on the given parameters.
Basic concepts of organic chemistry. Carbon stands out among all the elements in that its atoms can bond with each other in long chains or cycles. It is this property that allows carbon to form millions of compounds, the study of which is devoted to a whole field - organic chemistry.
The modern theory of the structure of molecules explains both a huge number of organic compounds and the dependence of the properties of these compounds on their chemical structure. It also fully confirms the basic principles of the theory of chemical structure, developed by the outstanding Russian scientist A.M. Butlerov. (NOT FACT WHAT IS NECESSARY).
Hybridization (chemistry) is a specific interaction of atomic orbitals in molecules.
Atoms (the smallest possible particle of any of the simplest chemicals called elements) are made up of nuclei and electrons that revolve around them. Electrons are not exactly corpuscles, but waves too, so they form a kind of clouds around the nuclei of atoms (some space in which electrons "live"). If the cloud of one electron overlaps with the cloud of another, then hybridization can occur - the electron clouds combine and two electrons begin to "dwell" in one common cloud. Since these electrons belong to different atoms, the atoms become bonded.
Orbital hybridization- the concept of mixing different, but close in energy, orbitals of a given atom, with the emergence of the same number of new hybrid orbitals, identical in energy and shape. Hybridization of atomic orbitals occurs when a covalent bond occurs between atoms. Orbital hybridization is very useful in explaining the shape of molecular orbitals and is an integral part of valence bond theory.
Chemical transformations of high molecular weight compounds. Polymer degradation reactions. Types of destruction.
There are three types of polymer reactions:
- reactions without changing the degree of polymerization (polymer-analogous transformations);
- reactions leading to its increase (structuring, block and graft copolymerization);
- reactions leading to a decrease in the degree of polymerization (chain rupture during polymer destruction).
Views:
Chemical destruction;
Oxidative destruction;
Oxidative destruction is observed in both heterochain and carbon chain polymers;
Destruction under the influence of physical influences
Thermal destruction
Photochemical destruction
Destruction under the influence of radioactive radiation. Under the influence of ionizing radiation, polymers undergo profound chemical and structural changes, leading to a change in the physicochemical and physicomechanical properties.
Mechanochemical destruction
Ticket number 5
1.Types of hybridization of atomic orbitals in organic compounds. sp 3 -, sp 2 -, sp - hybridization.
Atomic orbital Is a function that describes the density of an electron cloud at each point in space around the nucleus of an atom.
Hybridization types
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 engage in lone 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 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.
| Single (σ) | Double (σ + π) | Triple (σ + π + π) |
| С – С С – Н С – О H – Cl | C = O C = C O = O | С≡С С≡N N≡N |
Hybridization
If an atom is bonded to other atoms by EQUAL BONDS, but different types of orbitals are involved in their formation, then the HYBRIDIZATION method is used.
Example:The CH 4 molecule has the shape of a regular tetrahedron, in which all 4 bonds have the same length, strength, and are at the same angles to each other.
However, in a tetravalent carbon atom, electrons are located in three p-orbitals and one s-orbital. They are different in energy, shape and are located differently in space.
For explanation, the concept of HYBRIDIZATION is used:
From four atomic orbitals, 4 new ones are formed,
hybrid orbitals, which in space are located AT THE MAXIMUM DISTANCE OF EACH OTHER. It is a regular tetrahedron, the angles between bonds are 109 ° 29´.
Since one s and three p-shells participate in the formation of four bonds, this type of hybridization is denoted sp 3
Depending on the number and type of orbitals that take part in hybridization, the following types of hybridization are distinguished:
1) sp-hybridization. One s-orbital and one p-orbital are involved. The molecule has a linear structure, the bond angle is 180 0.
2) sp 2 -hybridization. One s-orbital and two p-orbitals are involved. The molecule is located in a plane (the ends of the hybrid orbitals are directed to the vertices of an equilateral triangle), the bond angle is 120 0.
3) sp 3 -hybridization. One s-orbital and three p-orbitals are involved. The molecule has a tetrahedral shape, the bond angle is 109.28 0.
How to determine the type of hybridization?
1. Hybridization involves sigma bonds and INDIVIDUAL IONIC PAIRS.
2. The total number of participating sigma bond orbitals + electron pairs = the number of hybrid orbitals and determines the type of hybridization.
Exercise: determine the type of hybridization of the carbon atom in the phosgene molecule.
O = C - Cl
1) carbon forms 2 single bonds (these are sigma bonds) and one double bond (sigma + pi). All 4 electrons of carbon participate in the formation of these bonds.
2) thus, THREE SIGMA bonds will take part in hybridization. it sp 2 - hybridization, the molecule has the form flat triangle. The pi-link is located perpendicular to the plane of this triangle.
HYBRIDIZATION- this is the phenomenon of interaction between molecular orbitals, which are close in energy and have common symmetry elements, with the formation of hybrid orbitals with lower energy.
The more fully the electron clouds that participate in chemical bonding overlap with each other in space, the less energy is possessed by the electrons in the overlapping region and making a bond, and the stronger the chemical bond between these atoms
Sometimes the bond between atoms is stronger than calculated. The atomic orbital is assumed to take on a shape that allows it to overlap more fully with the orbital of the neighboring atom. An atomic orbital can change its shape only by combining with other atomic orbitals of a different symmetry of the same atom. As a result of the combination of different orbitals (s, p, d), new intermediate atomic orbitals appear, which are called hybrid .
The rearrangement of various atomic orbitals into new orbitals averaged over shape is called hybridization .
The number of hybrid orbitals is equal to the number of original ones. So, with a combination of s- and p-orbitals (sp-hybridization), two hybrid orbitals appear, which are oriented at an angle of 180 ° to each other, Fig. 3, table. 5 and 6.
(s + p) -orbitals Two sp - orbitals Two sp-hybrid
orbitals
Figure 3 - sp - Hybridization of valence orbitals
Table 6 - Formation of hybrid orbitals
Table 7 - Formation of some molecules of V and VI periods
The chemical bond formed by the electrons of the hybrid orbitals is stronger than the bond with the participation of the electrons of the non-hybrid orbitals, since overlapping occurs to a greater extent during hybridization. Hybrid orbitals form only s-bonds.
Orbitals with similar energies can undergo hybridization. For atoms with a low nuclear charge, only s– and p –orbitals are suitable for hybridization. This is most typical for the elements of the second period of II - VI groups, tab. 6 and 7.
In groups from top to bottom with an increase in the radius of an atom, the ability to form covalent bonds weakens, the difference in the energies of s - and p-electrons increases, and the possibility of their hybridization decreases.
The electron orbitals involved in bond formation and their spatial orientation determine the geometric shape of the molecules.
Linear molecular shape. Compounds with a linear molecular shape are formed by overlapping:
1. Two s– orbitals (s - s bond): Н 2, Na 2, K 2, etc.
2. s - and p – orbitals (s - p bond): HC1, HBr, etc.
3. Two p - orbitals (p - p bond): F 2, C1 2, Br 2, etc.
s – s s – p р – р
Figure 4 - Linear molecules
The linear form of the molecules is also formed by the atoms of some elements of group II with hydrogen or halogen atoms (BeH 2, BeG 2, ZnG 2). Let us consider the formation of BeCl 2 molecules. The beryllium atom in an excited state has two unpaired electrons (2s l and 2p 1), therefore, sp-hybridization occurs, at which two sp-hybrid orbitals are formed, located relative to each other at an angle of 180 ° (see orbital hybridization). When beryllium interacts with halogens, two sp-hybrid orbitals of the beryllium atom overlap with the p-orbitals of two chlorine atoms, resulting in a linear molecule, Fig. 5.
Figure 5 - Linear molecule BeCl 2
Triangular shape of molecules takes place during the formation of boron and aluminum halides. An excited bot atom has three unpaired electrons (2s 1 and 2p 2). When chemical bonds are formed, sp 2 hybridization occurs and three sp 2 - hybrid orbitals are formed, which lie in the same plane and are oriented to each other at an angle of 120 °, Fig. 6.
(s + p + p) - three sp 2 - hybrid
orbital orbital
Figure 6 - sp 2 - Hybridization of valence orbitals (a) and
triangular molecule ВСl 3 (b)
When boron interacts with chlorine, three sp 2 -hybrid orbitals of the boron atom overlap with the p-orbitals of three chlorine atoms, resulting in a molecule having the shape of a flat triangle. The bond angle in the ВСl 3 molecule is 120 °.
Tetrahedral Molecule Shape typical for compounds of group IV elements of the main subgroup with halogens, hydrogen. So, a carbon atom in an excited state has four unpaired electrons (2s 1 and 2p 3), therefore, sp-hybridization occurs, in which four hybrid orbitals are formed, located at an angle of 109.28 ° to each other, Fig. 7.
(s + p + p + p) - four sp 3 -hybrid
orbital orbital
Figure 7 - sp 3 - Hybridization of valence orbitals (a) and
tetrahedral molecule СН 4 (b)
When four sp 3 -hybrid orbitals of a carbon atom and s-orbitals of four hydrogen atoms overlap, a tetrahedral methane molecule is formed. The bond angle is 109.28 °.
The considered geometric shapes of molecules (linear, triangular, tetrahedral) are ideal(Gillespie rule).
In contrast to the above compounds, the molecules of the elements of groups V and VI of the main subgroups have valence lone pairs of electrons, therefore the angles between the bonds turn out to be smaller in comparison with ideal molecules.
Pyramidal shape of molecules takes place during the formation of hydrogen compounds of group V elements of the main subgroup. When a chemical bond is formed, for example, at the nitrogen atom, as well as at the carbon atom, sp 3 -hybridization occurs and four sp 3 -hybrid orbitals are formed, which are oriented at an angle of 109.28 about to each other. But unlike the carbon atom at the nitrogen atom, not only one-electron orbitals are involved in hybridization(2p 3), but also two-electron(2s 2). Therefore, out of four sp 3 -hybrid orbitals, three have one electron each (one-electron orbital), these orbitals form bonds with three hydrogen atoms. The fourth orbital with a lone pair of electrons does not take part in the formation of a bond. The NH 3 molecule has the shape of a pyramid, Fig. eight.
Figure 8 - Pyramidal ammonia molecule
At the top of the pyramid is a nitrogen atom, and at the corners (triangle) of the base are hydrogen atoms. The bond angle is 107.3 °. The deviation of the angle from the tetrahedral (109.28 °) is due to the repulsion between the lone pair of electrons in the fourth sp 3 hybrid orbital and the bonding pairs in the other three orbitals, i.e. The sp 3 -hybrid orbital with a lone pair of electrons repels the other three orbitals of the N – H bond in the direction away from itself, reducing the angle to 107.3 °.
In accordance with the Gillespie rule: if the central atom belongs to the elements of the third or subsequent periods, and the terminal atoms belong to less electronegative elements than halogens, then the formation of bonds is carried out through pure p - orbitals and the bond angles become »90 °, therefore, for nitrogen analogs (P, As, Sb) orbital hybridization in the molecules of hydrogen compounds is not observed. For example, the formation of a phosphine molecule (PH 3) involves three unpaired p-electrons (3s 2 and 3p 3), the electron orbitals of which are located in three mutually perpendicular directions, and the s-electrons of three hydrogen atoms. The bonds are located along the three axes of the p-orbitals. The resulting molecules, like the NH 3 molecules, have a pyramidal shape, but unlike the NH 3 molecule, the bond angle in the PH 3 molecule is 93.3 °, and in the AsH 3 and SbH 3 compounds, respectively 91.8 and 91.3 °, Fig. 9 and tab. 4.
Figure 9 - Molecule PH 3
The lone pair of electrons will occupy a non-bonding s-orbital.
Angular shape of molecules form hydrogen compounds of Group VI elements of the main subgroup. The considered features of bond formation in compounds of Group V elements are also characteristic of hydrogen compounds of Group VI elements. So, in the water molecule, the oxygen atom, as well as the nitrogen atom, is in the sp 3 -hybridization state. Of the four sp 3 -hybrid orbits, two have one electron each, these orbitals form bonds with two hydrogen atoms.
The other two of the four sp 3 -hybrid orbitals each contain a lone pair of electrons and do not participate in the formation of a bond.
The Н 2 О molecule has an angular shape, the bond angle is 104.5 °. The deviation of the angle from the tetrahedral angle is to an even greater extent due to the repulsion from two lone pairs of electrons, Fig. ten.
Figure 10 - Angular water molecule
The angular shape of the molecules is H 2 S, H 2 Se, H 2 Te, only in analogs of oxygen, the formation of bonds in the connected H 2 E is carried out through pure p-orbitals(Gillespie rule), so the bond angles are »90 °. So, in molecules H 2 S, H 2 Se, H 2 Te, they are respectively equal to 92; 91; 89.5 °.
Table 8 - Molecules of hydrogen compounds of the elements of the 2nd period
Sp-hybridization
sp-hybridization takes place, for example, during the formation of halides Be, Zn, Co and Hg (II). In the valence state, all metal halides contain s and p-unpaired electrons at the corresponding energy level. When a molecule is formed, one s- and one p-orbital form two hybrid sp-orbitals at an angle of 180 °.
Fig. 3 sp hybrid orbitals
Experimental data show that all Be, Zn, Cd and Hg (II) halides are linear and both bonds have the same length.
sp 2 -hybridization
As a result of hybridization of one s-orbital and two p-orbitals, three hybrid sp 2 -orbitals are formed, located in the same plane at an angle of 120 ° to each other. This is, for example, the configuration of the BF 3 molecule:
Fig. 4 sp 2 -hybridization
sp 3 -hybridization
sp 3 -hybridization is characteristic of carbon compounds. As a result of hybridization of one s-orbital and three
p-orbitals, four hybrid sp 3 -orbitals are formed, directed to the vertices of the tetrahedron with an angle between the orbitals of 109.5 o. Hybridization manifests itself in the complete equivalence of the bonds of the carbon atom with other atoms in compounds, for example, in CH 4, CCl 4, C (CH 3) 4, etc.
Fig. 5 sp 3 -hybridization
If all hybrid orbitals are bonded to the same atoms, then the bonds are no different from each other. In other cases, there are small deviations from the standard bond angles. For example, in the H2O water molecule oxygen is sp 3 -hybrid, located in the center of an irregular tetrahedron, at the vertices of which two hydrogen atoms and two lone pairs of electrons "look" (Fig. 2). The shape of the molecule is angular when viewed from the centers of the atoms. The bond angle HOH is 105 о, which is quite close to the theoretical value of 109 о.
Fig. 6 sp 3 -hybridization of oxygen and nitrogen atoms in molecules a) H 2 O and b) NCl 3.
If hybridization (“alignment” of O-H bonds) did not occur, the HOH bond angle would be 90 °, because hydrogen atoms would be attached to two mutually perpendicular p-orbitals. In this case, our world would probably look completely different.
Hybridization theory explains the geometry of the ammonia molecule. As a result of hybridization of 2s and three 2p nitrogen orbitals, four hybrid sp 3 orbitals are formed. The configuration of the molecule is a distorted tetrahedron, in which three hybrid orbitals participate in the formation of a chemical bond, and the fourth with a pair of electrons does not. The angles between N-H bonds are not equal to 90 ° as in a pyramid, but they are not equal to 109.5 °, corresponding to a tetrahedron.
Fig. 7 sp 3 - hybridization in the ammonia molecule
When ammonia interacts with a hydrogen ion, as a result of the donor-acceptor interaction, an ammonium ion is formed, the configuration of which is a tetrahedron.
Hybridization also explains the difference in the angle between the O - H bonds in the angular water molecule. As a result of hybridization of the 2s and three 2p oxygen orbitals, four hybrid sp 3 orbitals are formed, of which only two are involved in the formation of a chemical bond, which leads to a distortion of the angle corresponding to the tetrahedron.
Fig. 8 sp 3 -hybridization in the water molecule
Hybridization can include not only s and p, but also d and f orbitals.
With sp 3 d 2 -hybridization, 6 equivalent clouds are formed. It is observed in compounds such as 4-, 4-. In this case, the molecule has the configuration of an octahedron.
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