Chemical Communications -chemical bond - mutual attraction of atoms leading to the formation of molecules and crystals.
Currently, it is not enough to indicate the presence of a chemical bond, and it is necessary to clarify its type: ionic, covalent, dipole-dipole, metal Covalent communication It is formed at the expense of general electronic pairs arising in the shells of associated atoms.
It can be formed by atoms of one taking place and then it is non-polar; For example, such a covalent bond exists in the molecules of one-element gases H 2, O 2, N 2, CL 2, etc., etc.
Covalent bond can be formed by atoms of different elements similar to chemical character, and then it is polar; For example, such a covalent bond exists in H 2 O, NF 3, CO 2 molecules. Covalent bond is formed between atoms of elements with electronegative character
Electricity- this is the ability of atoms chemical element Press the general electronic couples involved in the formation of a chemical connection
Metal communication It occurs as a result of partial delocalization of valence electrons, which are quite freely moving in the lattice of metals, electrostatically interacting with positively charged ions. Communication forces are not localized and not directed, and delocalized electrons determine high heat and electrical conductivity.
Ion connection is a particular case of covalent, when the resulting electron pair fully belongs to a more electronegative atom that becomes an anion. The basis for allocating this connection to a separate type is the fact that compounds with such a bond can be described in the electrostatic approximation, counting ion communication due to attraction of positive and negative ions. The interaction of ions of the opposite sign does not depend on the direction, and the Coulomb forces do not have the property of saturation. So every ion in ion connection attracts such a number of ions of the opposite sign to form a crystal lattice ion type. There are no molecules in the ion crystal. Each ion is surrounded by a certain number of ions of another sign (coordination number of ion). Ion pairs can exist in a gaseous state in the form of polar molecules. In the gaseous state, NaCl has a dipole moment of ~ 3 ∙ 10 -29 KL ∙ M, which corresponds to a displacement of 0.8 charge of an electron for a communication length of 0.236 nm from Na to Cl, i.e. Na 0.8+ CL 0.8-.
Hydrogen bond. Its education is due to the fact that as a result of a strong displacement electronic couple To the electronegative atom, a hydrogen atom, which has an effective positive charge, can interact with another electronegative atom (F, O, N, less frequent cl, br, s). The energy of such electrostatic interaction is 20-100 kJ ∙ Mol -1. Hydrogen bonds can be in- and intermolecular. Intramolecular hydrogen bond is formed, for example, in acetylacetone and is accompanied by a circuit of the cycle
Carboxylic acid molecules in non-polar solvents are dimerized due to two intermolecular hydrogen ties
An extremely important role to hydrogen bonds in biological macromolecules, such inorganic compounds as H 2 O, H 2 F 2, NH 3. Due to hydrogen bonds, water is characterized as high compared to H 2 E (E \u003d S, SE, TE) with melting and boiling temperatures. If hydrogen bonds Absent, the water would melt at -100 ° C, and boiled at -80 ° C.
Van der Waalsov (intermolecular bond - the most universal view of the intermolecular connection is due to the dispersion forces (induced dipole - induced dipole), induction interaction (permanent dipole - induced dipole) and orientational interaction (permanent dipole - permanent dipole). The energy of the van der Waals bond is less hydrogen and is 2-20 kJ ∙ Mol -1.
Option 1
1. Determine the type of chemical bond in the compounds N₂, KF, HF, NH₃ and HSS. Write structural and electronic formulas NH₃ and HF.
2. Picture electronic formulas of the neutral atom and lithium ion. What does the structure of these particles differ?
LI: 1S2 2S1 - a neutral lithium atom
Lithium cation (gave one electron): Li +: 1s2 2s0
3. Determine the type of crystal lattice characteristic of each of the following substances: potassium chloride, graphite, sugar, iodine, diamond.
KCL-ion lattice, atomic, sugar - molecular, iodine - molecular, diamond - atomic.
Option 2.
1. From the above formulas of substances, write only the formulas of the compounds with covalent polar connections: CO₂, PH₃, H₂, OF₂, O₂, KF, NaCl.
CO2, PH3, OF2
2. Make electronic formulas of chlorine molecules CL₂, hydrogen sulfide H₂s and phosphine PH₃. 
3. On specific examples, compare physical properties Substances having a molecular and crystal lattice. 
Option 3.
1. Determine the type of chemical bond in compounds SO₃, NCL₃, CLF₃, BR₂, H₂O and NaCl.
2. Make electronic formulas of iodine molecules I₂, water and methane CH₄. 
3. On specific examples, show how some physical properties of substances depend on the type of their crystal lattice. 
Option 4.
1. From the above formulas of substances, write only the formulas of the compounds with covalent non-polar connections: I₂, HCl, O₂, NH₃, H₂O, N₂, CL₂, PH₃, NANO₃.
I2, O2, N2, CL2
"Chemistry. Grade 8". O.S. Gabrielyan.
The formation of chemical bond between the atoms of the elements
Question 1 (1).
Since the values \u200b\u200bof hydrogen EO and phosphorus are the same, then the chemical bond in the pH 3 molecule will be covalent notolary.
Question 2 (2).
І. a) in the molecule s 2 covalent Nonolaurbecause It is formed by atoms of the same element. The communication scheme will be as follows: sulfur - element the main subgroup VI group. Sulfur atoms have 6 electrons on the outer shell. Unpaired electrons will be two (8 - 6 \u003d 2). Denote by external electrons, then the sulfur molecule formation scheme will look at:
b) in the molecule k 2 o Communication ionicBecause it is formed by atoms of metal and nonmetal elements.
Potassium - element of the first group of the main subgroup, metal. It is easier to pay 1 electron to it, than to take the missing 7 electrons:
Oxygen - element of the main subgroup of the sixth group, nonmetall. Its atom is easier to accept 2 electron, which lacks until the completion of the level than to give 6 electrons:
We will find the smallest common multiple between the charges of the formed ions, it is equal to 2 (2. 1). So that potassium atoms have given 2 electrons, they need to be taken 2 so that the oxygen atoms can take 2 electrons, it is necessary to take 1 atom, so the potassium oxide formation scheme will be: 
c) in the H 2 S molecule covalent polarbecause it is formed by atoms of elements with different EO. The scheme of the formation of a chemical communication will be as follows:
Sulfur - element of the main subgroup of the group VI. Its atoms have 6 electrons on the outer shell. Unpaired electrons will be 2 (8 - 6 \u003d 2).
Hydrogen is an element of the main subgroup of 1 of the group. Its atoms contain 1 electron on the outer shell. It is not part of 1 electron (for the hydrogen atom, a two-electron level is completed).
Denote the external electrons of sulfur and hydrogen atoms, respectively: 
or
H-S-H
In the sulfide molecule, general electronic pairs are shifted towards a more electronegative atom - sulfur: 
1. a) In the molecule N 2, the connection is covalent, non-polar, because it is formed by atoms of the same element. The formation scheme is as follows:
Nitrogen is the element of the main subgroup of the group. Its atoms have 5 electrons on the outer shell. Unpaired electrons three (8 - 5 \u003d h).
Denote by the external electrons of the nitrogen atom points: 
b) In the Li 3 N molecule, the ionic connection is because it is formed by atoms of metal elements and non-metal.
Lithium - element of the main subgroup of the group, metal. It is easier to pay 1 electron to it, than to take the missing 7 electrons: 
Nitrogen is an element of the main subgroup of the group V, nonmetall. It is easier to accept its electron, which is not enough until the external level is completed than to give five electrons from the external level: 
We find the smallest common multiple between the charges of the ions formed, it
equally 3 (3: 1 \u003d 3). In order for lithium atoms to be given by the electron, it is necessary to make a nitrogen atoms to take the US electron, only one atom is needed:
c) in the NCl 3 molecule 3, covalent polar communication, because It is formed by the atoms of non-metal elements with various EO values. The formation scheme is as follows:
Nitrogen is the element of the main subgroup of the group. Its atoms have 5 electrons on the outer shell. Unpaired electrons will be three (8-5 \u003d 3).
Chlorine is the element of the main subgroup of the group VII. Its atoms contain 7 electrons on the outer shell. Notparable remains
1 electron (8 - 7 \u003d 1). Denote the external electrons of nitrogen and chlorine atoms, respectively: 
General electronic pairs are shifted to nitrogen atom, as more electronegative: 
Question 3 (3).
Communication in the HCl molecule is less polar, than in the HF molecule, because in a series of changes in EO chlorine and hydrogen are less removed from each other than fluorine and hydrogen.
Question 4 (4).
Covalent chemical bond is formed by generalizing external electrons. In terms of the number of common electronic pairs, it can be single, double or triple, and in electronegativity, forming it atoms - covalent polar and covalent non-polar.
Example 1. Set which of the listed below the molecules F 2, HF, BEF 2, BF 3, PF 3, CF 4 are polar.
Decision: Diatectural molecules formed by the same atoms (F 2) are not polar, and different (HF) - polar. The polarity of molecules consisting of three or more atoms is determined by their structure. The structure of BEF 2 molecules, BF 3, CF 4 is explained with the involvement of the representations of hybridization atomic orbitals (respectively, Sp-, SP 2 - and SP 3 - hybridization). Geometric amount of dipole moments e-F connections In these molecules is zero, so they are not too polar.
In the formation of the PF 3 molecule, the three p-orbitals of the phosphorus atom with electronic p-orbitals of the three fluorine atoms take place. As a result, this molecule has a pyramid. We arrive at similar conclusion if used to explain the structure of the PF 3 molecules on SP 3 - hybridization with the participation of a viable electronic pair. Total dipole moment references P-F It is not equal to zero and this polar molecule. The final results of the above analysis are presented in the table.
Example 2. Destermine the valence capabilities of oxygen and selenium atoms.
Decision. Electronic formula of an oxygen atom 1S 2 2S 2 2P 4. On the outer electronic layer of this atom there are only six electrons, two of which are unpaired. Therefore, in its compounds oxygen duvelanet. This is the only possible valence condition of the oxygen atom, since the elements of the second period are absent d.-Ibed.
In the fourth period, the selenium atom on the external electronic layer besides s.- I. r- orbitals are also available d.- orbitals, for which when excited, can proceed s.- I. r- electrons. As a result, as in the case of a sulfur atom (Fig. 5.9), selenium in its compounds may not only be bivalent, but also four- I. hexavalent.
Example 3.Position the Molecules NH 3, H 2 O, SIH 4, PH 3 in the order of increasing chemical length element-hydrogen.
Decision: The length of the chemical bond increases with an increase in the radius of the atom associated with the hydrogen atom. In order to increase the length of the communication are arranged as follows: H 2 O, NH 3, pH 3, Sih 4.
Example 4.Position O 2, N 2, CL 2, BR 2 molecules in an increase in chemical bond energy.
Decision. Communication energy increases with a decrease in its length and increase the multiplicity of communication. Therefore, a single bond in the chlorine molecule is more durable than in a bromine molecule. Double bond takes place in the oxygen molecule. This connection is stronger single touch Chlorine molecules, but weaker the triple bond in the nitrogen molecule. As a result, the chemical bond energy increases in a row: Br 2, Cl 2, O 2, N 2.
Example 5.Set the type of crystal lattice in the following substances: graphite, zinc, zinc chloride, carbon dioxide.
Decision. Graphite, as well as a diamond, has an atomic crystal lattice, and zinc - metal crystal grille. Zinc chloride has an ionic crystal lattice. In the nodes of the crystal lattice of solid carbon oxide (IV) there are molecules of CO 2, therefore this substance in a solid state has a molecular crystalline grid.
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