The first of these is the formation of an ionic bond. (The second is education, which will be discussed below). When an ionic bond is formed, a metal atom loses electrons, and a nonmetal atom gains. For example, consider the electronic structure of sodium and chlorine atoms:
Na 1s 2 2s 2 2 p6 3 s 1 - one electron in the outer level
Cl 1s 2 2s 2 2 p6 3 s2 3 p 5 — seven electrons in the outer level
If the sodium atom donates its single 3s electron to the chlorine atom, the octet rule will hold for both atoms. The chlorine atom will have eight electrons in the outer third layer, and the sodium atom will also have eight electrons in the second layer, which has now become outer:
Na + 1s 2 2s 2 2 p 6
Cl - 1s 2 2s 2 2 p6 3 s2 3 p6 - eight electrons in the outer level
At the same time, the nucleus of the sodium atom still contains 11 protons, but the total number of electrons has decreased to 10. This means that the number of positively charged particles is one more than the number of negatively charged ones, so the total charge of the "atom" of sodium is +1.
An "atom" of chlorine now contains 17 protons and 18 electrons and has a charge of -1.
Charged atoms formed as a result of the loss or gain of one or more electrons are called ions. Positively charged ions are called cations, and the negatively charged ones are called anions.
Cations and anions, having opposite charges, are attracted to each other by electrostatic forces. This attraction of oppositely charged ions is called ionic bonding.
. It occurs in compounds formed by a metal and one or more non-metals.
The following compounds meet this criterion and are ionic in nature: MgCl 2, Fel 2, CuF, Na 2 0, Na 2 S0 4, Zn(C 2 H 3 0 2) 2.
There is another way to represent ionic compounds:
In these formulas, dots show only the electrons located on the outer shells ( valence electrons ). Such formulas are called Lewis formulas in honor of the American chemist G. N. Lewis, one of the founders (along with L. Pauling) of the theory of chemical bonding.
The transfer of electrons from a metal atom to a non-metal atom and the formation of ions are possible due to the fact that non-metals have a high electronegativity, and metals have a low one.
Due to the strong attraction of ions to each other, ionic compounds are mostly solid and have a rather high melting point.
An ionic bond is formed by the transfer of electrons from a metal atom to a nonmetal atom. The resulting ions are attracted to each other by electrostatic forces.
All chemical compounds are formed through the formation of a chemical bond. And depending on the type of connecting particles, several types are distinguished. The most basic- these are covalent polar, covalent non-polar, metallic and ionic. Today we will talk about ionic.
In contact with
What are ions
It is formed between two atoms - as a rule, provided that the difference in electronegativity between them is very large. Electronegativity of atoms and ions is estimated according to the Polling scale.
Therefore, in order to correctly consider the characteristics of compounds, the concept of ionicity was introduced. This characteristic allows you to determine how many percent a particular bond is ionic.
The compound with the highest ionicity is cesium fluoride, in which it is approximately 97%. Ionic bond is characteristic for substances formed by metal atoms located in the first and second groups of the table D.I. Mendeleev, and atoms of non-metals in the sixth and seventh groups of the same table.
Note! It is worth noting that there is no compound in which the relationship is exclusively ionic. For currently discovered elements, it is impossible to achieve such a large difference in electronegativity as to obtain a 100% ionic compound. Therefore, the definition of an ionic bond is not entirely correct, since compounds with partial ionic interaction are actually considered.
Why was this term introduced, if such a phenomenon does not really exist? The fact is that this approach helped to explain many nuances in the properties of salts, oxides and other substances. For example, why are they highly soluble in water, and their solutions are capable of conducting electricity. It cannot be explained from any other position.
Mechanism of Education
The formation of an ionic bond is possible only if two conditions are met: if the metal atom participating in the reaction is able to easily donate electrons that are at the last energy level, and the non-metal atom is able to accept these electrons. Metal atoms are inherently reducing agents, that is, they are capable of recoil of electrons.
This is due to the fact that at the last energy level in the metal there can be from one to three electrons, and the radius of the particle itself is quite large. Therefore, the force of interaction of the nucleus with electrons at the last level is so small that they can easily leave it. With non-metals, the situation is completely different. They have small radius, and the number of own electrons at the last level can be from three to seven.
And the interaction between them and the positive nucleus is quite strong, but any atom tends to complete the energy level, so non-metal atoms tend to get the missing electrons.
And when two atoms meet - a metal and a non-metal, there is a transition of electrons from the metal atom to the non-metal atom, and a chemical interaction is formed.
Connection diagram
The figure clearly shows how the formation of an ionic bond is carried out. Initially, there are neutrally charged atoms of sodium and chlorine.
The first has one electron in the last energy level, the second has seven. Next, an electron passes from sodium to chlorine and the formation of two ions. Which combine with each other to form a substance. What is an ion? An ion is a charged particle that the number of protons is not equal to the number of electrons.
Differences from the covalent type
The ionic bond, due to its specificity, has no direction. This is due to the fact that the electric field of an ion is a sphere, while it decreases or increases uniformly in one direction, obeying the same law.
Unlike covalent, which is formed due to the overlap of electron clouds.
The second difference is that covalent bond is saturated. What does it mean? The number of electronic clouds that can take part in the interaction is limited.
And in the ion one, due to the fact that the electric field has a spherical shape, it can combine with an unlimited number of ions. So, we can say that it is not saturated.
It can also be characterized by several other properties:
- The bond energy is a quantitative characteristic, and it depends on the amount of energy that must be expended to break it. It depends on two criteria - bond length and ion charge involved in its formation. The bond is stronger, the shorter its length and the greater the charges of the ions that form it.
- Length - this criterion has already been mentioned in the previous paragraph. It depends solely on the radius of the particles involved in the formation of the compound. The radius of atoms changes as follows: decreases in period with increasing serial number and increases in the group.
Substances with an ionic bond
It is characteristic of a significant number of chemical compounds. This is a large part of all salts, including the well-known table salt. It occurs in all compounds where there is a direct contact between metal and non-metal. Here are some examples of substances with an ionic bond:
- sodium and potassium chlorides,
- cesium fluoride,
- magnesium oxide.
It can also appear in complex compounds.
For example, magnesium sulfate.
Here is the formula of a substance with ionic and covalent bonds:
An ionic bond will form between oxygen and magnesium ions, but sulfur and are interconnected already with the help of a covalent polar one.
From which we can conclude that the ionic bond is characteristic of complex chemical compounds.
What is an ionic bond in chemistry
Types of chemical bond - ionic, covalent, metallic
Conclusion
Properties directly dependent on the device crystal lattice. Therefore, all compounds with an ionic bond are highly soluble in water and other polar solvents, conduct and are dielectrics. At the same time, they are quite refractory and brittle. The properties of these substances are often used in the construction of electrical appliances.
Atoms of most elements do not exist separately, as they can interact with each other. In this interaction, more complex particles are formed.
The nature of the chemical bond is the action of electrostatic forces, which are the forces of interaction between electric charges. Electrons and atomic nuclei have such charges.
Electrons located at the outer electronic levels (valence electrons), being farthest from the nucleus, interact with it the weakest, and therefore are able to break away from the nucleus. They are responsible for the binding of atoms to each other.
Types of interaction in chemistry
The types of chemical bond can be represented as the following table:
Ionic bond characteristic
The chemical interaction that is formed due to ion attraction having different charges is called ionic. This happens if the bonded atoms have a significant difference in electronegativity (that is, the ability to attract electrons) and the electron pair goes to a more electronegative element. The result of such a transition of electrons from one atom to another is the formation of charged particles - ions. There is an attraction between them.
have the lowest electronegativity typical metals, and the largest are typical non-metals. Ions are thus formed by interactions between typical metals and typical non-metals.
Metal atoms become positively charged ions (cations), donating electrons to external electronic levels, and non-metals accept electrons, thus turning into negatively charged ions (anions).
Atoms move into a more stable energy state, completing their electronic configurations.
The ionic bond is non-directional and not saturable, since the electrostatic interaction occurs in all directions, respectively, the ion can attract ions of the opposite sign in all directions.
The arrangement of ions is such that around each is a certain number of oppositely charged ions. The concept of "molecule" for ionic compounds doesn't make sense.
Examples of Education
The formation of a bond in sodium chloride (nacl) is due to the transfer of an electron from the Na atom to the Cl atom with the formation of the corresponding ions:
Na 0 - 1 e \u003d Na + (cation)
Cl 0 + 1 e \u003d Cl - (anion)
In sodium chloride, there are six chloride anions around the sodium cations, and six sodium ions around each chloride ion.
When an interaction is formed between atoms in barium sulfide, the following processes occur:
Ba 0 - 2 e \u003d Ba 2+
S 0 + 2 e \u003d S 2-
Ba donates its two electrons to sulfur, resulting in the formation of sulfur anions S 2- and barium cations Ba 2+ .
metal chemical bond
The number of electrons in the outer energy levels of metals is small; they easily break away from the nucleus. As a result of this detachment, metal ions and free electrons are formed. These electrons are called "electron gas". Electrons move freely throughout the volume of the metal and are constantly bound and detached from atoms.
The structure of the metal substance is as follows: the crystal lattice is the backbone of the substance, and electrons can move freely between its nodes.
The following examples can be given:
Mg - 2e<->Mg2+
Cs-e<->Cs+
Ca-2e<->Ca2+
Fe-3e<->Fe3+
Covalent: polar and non-polar
The most common type of chemical interaction is a covalent bond. The electronegativity values of the interacting elements do not differ sharply, in connection with this, only a shift of the common electron pair to a more electronegative atom occurs.
Covalent interaction can be formed by the exchange mechanism or by the donor-acceptor mechanism.
The exchange mechanism is realized if each of the atoms has unpaired electrons in the outer electronic levels, and the overlap of atomic orbitals leads to the appearance of a pair of electrons that already belongs to both atoms. When one of the atoms has a pair of electrons on the outer electronic level, and the other has a free orbital, then when the atomic orbitals overlap, the electron pair is socialized and the interaction occurs according to the donor-acceptor mechanism.
Covalent are divided by multiplicity into:
- simple or single;
- double;
- triple.
Doubles provide the socialization of two pairs of electrons at once, and triples - three.
According to the distribution of electron density (polarity) between the bonded atoms, the covalent bond is divided into:
- non-polar;
- polar.
A non-polar bond is formed by the same atoms, and a polar bond is formed by electronegativity different.
The interaction of atoms with similar electronegativity is called a non-polar bond. The common pair of electrons in such a molecule is not attracted to any of the atoms, but belongs equally to both.
The interaction of elements differing in electronegativity leads to the formation of polar bonds. Common electron pairs with this type of interaction are attracted by a more electronegative element, but do not completely transfer to it (that is, the formation of ions does not occur). As a result of such a shift in the electron density, partial charges appear on atoms: on a more electronegative one, a negative charge, and on a less electronegative one, a positive one.
Properties and characteristics of covalence
The main characteristics of a covalent bond:
- The length is determined by the distance between the nuclei of the interacting atoms.
- Polarity is determined by the displacement of the electron cloud to one of the atoms.
- Orientation - the property to form space-oriented bonds and, accordingly, molecules that have certain geometric shapes.
- Saturation is determined by the ability to form a limited number of bonds.
- Polarizability is determined by the ability to change polarity under the influence of an external electric field.
- The energy required to break a bond, which determines its strength.
Molecules of hydrogen (H2), chlorine (Cl2), oxygen (O2), nitrogen (N2) and many others can be an example of a covalent non-polar interaction.
H + H → H-H the molecule has a single non-polar bond,
O: + :O → O=O the molecule has a double nonpolar,
Ṅ: + Ṅ: → N≡N the molecule has a triple non-polar.
Molecules of carbon dioxide (CO2) and carbon monoxide (CO) gas, hydrogen sulfide (H2S), hydrochloric acid (HCL), water (H2O), methane (CH4), sulfur oxide (SO2) and many others can be cited as examples of the covalent bond of chemical elements. .
In the CO2 molecule, the relationship between carbon and oxygen atoms is covalent polar, since the more electronegative hydrogen attracts electron density to itself. Oxygen has two unpaired electrons in the outer level, while carbon can provide four valence electrons to form an interaction. As a result, double bonds are formed and the molecule looks like this: O=C=O.
In order to determine the type of bond in a particular molecule, it is enough to consider its constituent atoms. Simple substances metals form a metallic one, metals with non-metals form an ionic one, simple substances non-metals form a covalent non-polar one, and molecules consisting of different non-metals are formed by means of a covalent polar bond.
Back forward
Attention! The slide preview is for informational purposes only and may not represent the full extent of the presentation. If you are interested in this work, please download the full version.
Lesson Objectives:
- To form the concept of chemical bonds using the example of an ionic bond. To achieve an understanding of the formation of an ionic bond as an extreme case of a polar one.
- During the lesson, ensure the assimilation of the following basic concepts: ions (cation, anion), ionic bond.
- To develop the mental activity of students through the creation of a problem situation when studying new material.
Tasks:
- learn to recognize the types of chemical bonds;
- repeat the structure of the atom;
- to investigate the mechanism of formation of ionic chemical bond;
- teach how to draw up formation schemes and electronic formulas of ionic compounds, reaction equations with the designation of the transition of electrons.
Equipment Keywords: computer, projector, multimedia resource, periodic system of chemical elements D.I. Mendeleev, table "Ionic bond".
Lesson type: Formation of new knowledge.
Type of lesson: multimedia lesson.
X one lesson
I.Organizing time.
II . Checking homework.
Teacher: How can atoms take on stable electronic configurations? What are the ways of forming a covalent bond?
Student: Polar and non-polar covalent bonds are formed by the exchange mechanism. The exchange mechanism includes cases when one electron is involved in the formation of an electron pair from each atom. For example, hydrogen: (slide 2)
The bond arises due to the formation of a common electron pair due to the union of unpaired electrons. Each atom has one s-electron. The H atoms are equivalent and the pairs equally belong to both atoms. Therefore, the formation of common electron pairs (overlapping p-electron clouds) occurs during the formation of the F 2 molecule. (slide 3)
H record · means that the hydrogen atom has 1 electron on the outer electron layer. The record shows that there are 7 electrons on the outer electron layer of the fluorine atom.
During the formation of the N 2 molecule. 3 common electron pairs are formed. The p-orbitals overlap. (slide 4)
The bond is called non-polar.
Teacher: We have now considered cases when molecules of a simple substance are formed. But there are many substances around us, a complex structure. Let's take a hydrogen fluoride molecule. How does the formation of a connection take place in this case?
Student: When a hydrogen fluoride molecule is formed, the orbital of the s-electron of hydrogen and the orbital of the p-electron of fluorine H-F overlap. (slide 5)
The bonding electron pair is shifted to the fluorine atom, resulting in the formation dipole. Connection called polar.
III. Knowledge update.
Teacher: A chemical bond arises as a result of changes that occur with the outer electron shells of the connecting atoms. This is possible because the outer electron layers are not complete in elements other than inert gases. The chemical bond is explained by the desire of atoms to acquire a stable electronic configuration, similar to the configuration of the "nearest" inert gas to them.
Teacher: Write down a diagram of the electronic structure of the sodium atom (at the blackboard). (slide 6)
Student: To achieve the stability of the electron shell, the sodium atom must either give up one electron or accept seven. Sodium will easily give up its electron far from the nucleus and weakly bound to it.
Teacher: Make a diagram of the recoil of an electron.
Na° - 1ē → Na+ = Ne
Teacher: Write down a diagram of the electronic structure of the fluorine atom (at the blackboard).
Teacher: How to achieve the completion of the filling of the electronic layer?
Student: To achieve the stability of the electron shell, the fluorine atom must either give up seven electrons or accept one. It is energetically more favorable for fluorine to accept an electron.
Teacher: Make a scheme for receiving an electron.
F° + 1ē → F- = Ne
IV. Learning new material.
The teacher addresses a question to the class in which the task of the lesson is set:
Are there other options in which atoms can take on stable electronic configurations? What are the ways of formation of such connections?
Today we will consider one of the types of bonds - ionic bonds. Let us compare the structure of the electron shells of the already named atoms and inert gases.
Conversation with the class.
Teacher: What charge did the sodium and fluorine atoms have before the reaction?
Student: The atoms of sodium and fluorine are electrically neutral, because. the charges of their nuclei are balanced by electrons revolving around the nucleus.
Teacher: What happens between atoms when giving and receiving electrons?
Student: Atoms acquire charges.
The teacher gives explanations: In the formula of an ion, its charge is additionally recorded. To do this, use the superscript. In it, a number indicates the amount of charge (they do not write a unit), and then a sign (plus or minus). For example, a Sodium ion with a charge of +1 has the formula Na + (read "sodium plus"), a Fluorine ion with a charge of -1 - F - ("fluorine minus"), a hydroxide ion with a charge of -1 - OH - (" o-ash-minus"), a carbonate ion with a charge of -2 - CO 3 2- ("tse-o-three-two-minus").
In the formulas of ionic compounds, first write down, without indicating the charges, positively charged ions, and then - negatively charged. If the formula is correct, then the sum of the charges of all ions in it is equal to zero.
positively charged ion called a cation, and a negatively charged ion-anion.
Teacher: We write the definition in workbooks:
And he is a charged particle into which an atom turns into as a result of receiving or giving off electrons.
Teacher: How to determine the charge of the calcium ion Ca 2+?
Student: An ion is an electrically charged particle formed as a result of the loss or gain of one or more electrons by an atom. Calcium has two electrons in the last electronic level, the ionization of a calcium atom occurs when two electrons are given away. Ca 2+ is a doubly charged cation.
Teacher: What happens to the radii of these ions?
During the transition electrically neutral atom into an ionic state, the particle size changes greatly. An atom, giving up its valence electrons, turns into a more compact particle - a cation. For example, during the transition of a sodium atom to the Na+ cation, which, as indicated above, has a neon structure, the radius of the particle is greatly reduced. The radius of an anion is always greater than the radius of the corresponding electrically neutral atom.
Teacher: What happens to oppositely charged particles?
Student: Oppositely charged sodium and fluorine ions, resulting from the transition of an electron from a sodium atom to a fluorine atom, are mutually attracted and form sodium fluoride. (slide 7)
Na + + F - = NaF
The scheme of formation of ions that we have considered shows how a chemical bond is formed between the sodium atom and the fluorine atom, which is called ionic.
Ionic bond- a chemical bond formed by the electrostatic attraction of oppositely charged ions to each other.
The compounds that form in this case are called ionic compounds.
V. Consolidation of new material.
Tasks to consolidate knowledge and skills
1. Compare the structure of the electron shells of the calcium atom and the calcium cation, the chlorine atom and the chloride anion:
Comment on the formation of an ionic bond in calcium chloride:
2. To complete this task, you need to divide into groups of 3-4 people. Each member of the group considers one example and presents the results to the whole group.
Students response:
1. Calcium is an element of the main subgroup of group II, a metal. It is easier for its atom to donate two outer electrons than to accept the missing six:
2. Chlorine is an element of the main subgroup of group VII, a non-metal. It is easier for its atom to accept one electron, which it lacks before the completion of the outer level, than to give up seven electrons from the outer level:
3. First, find the least common multiple between the charges of the formed ions, it is equal to 2 (2x1). Then we determine how many calcium atoms need to be taken so that they donate two electrons, that is, one Ca atom and two CI atoms must be taken.
4. Schematically, the formation of an ionic bond between calcium and chlorine atoms can be written: (slide 8)
Ca 2+ + 2CI - → CaCI 2
Tasks for self-control
1. Based on the scheme for the formation of a chemical compound, make up an equation for a chemical reaction: (slide 9)
2. Based on the scheme for the formation of a chemical compound, make up an equation for a chemical reaction: (slide 10)
3. A scheme for the formation of a chemical compound is given: (slide 11)
Choose a pair of chemical elements whose atoms can interact in accordance with this scheme:
A) Na And O;
b) Li And F;
V) K And O;
G) Na And F
| Structural chemistry | |
|---|---|
| Chemical bond: | Aromaticity | Covalent bond | Ionic bond| Metal connection | Hydrogen bond | Donor-acceptor bond | Tautomerism |
| Structure display: | Functional group | Structural formula | Chemical formula | ligand |
| Electronic properties: | Electronegativity | Electron affinity | Ionization energy | Dipole | Octet Rule |
| Stereochemistry: | Asymmetric atom | Isomerism | Configuration | Chirality | Conformation |
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See what "Ionic chemical bond" is in other dictionaries:
The bond between atoms in a molecule or mol. connection, arising as a result of either the transfer of an electron from one atom to another, or the socialization of electrons by a pair (or group) of atoms. The forces leading to X. s. are Coulomb, but X. s. describe within... Physical Encyclopedia
CHEMICAL BOND- interaction of atoms, in which electrons belonging to two different atoms (groups) become common (socialized) for both atoms (groups), causing their combination into molecules and crystals. There are two main types of X. s .: ionic ... ... Great Polytechnic Encyclopedia
CHEMICAL BOND The mechanism by which atoms combine to form molecules. There are several types of such a bond, based either on the attraction of opposite charges, or on the formation of stable configurations through the exchange of electrons. ... ... Scientific and technical encyclopedic dictionary
chemical bond- CHEMICAL BOND, the interaction of atoms, causing their connection into molecules and crystals. The forces acting during the formation of a chemical bond are mainly electrical in nature. The formation of a chemical bond is accompanied by a rearrangement ... ... Illustrated Encyclopedic Dictionary
- ... Wikipedia
Mutual attraction of atoms, leading to the formation of molecules and crystals. It is customary to say that in a molecule or in a crystal between neighboring atoms there are ch. The valency of an atom (which is discussed in more detail below) indicates the number of bonds ... Great Soviet Encyclopedia
chemical bond- mutual attraction of atoms, leading to the formation of molecules and crystals. The valence of an atom shows the number of bonds formed by a given atom with neighboring ones. The term "chemical structure" was introduced by Academician A. M. Butlerov in ... ... Encyclopedic Dictionary of Metallurgy
The interaction of atoms, which determines their connection into molecules and crystals. This interaction leads to a decrease in the total energy of the resulting molecule or crystal compared to the energy of non-interacting atoms and is based on ... ... Big encyclopedic polytechnic dictionary
Covalent bond on the example of a methane molecule: a complete external energy level for hydrogen (H) 2 electrons, and for carbon (C) 8 electrons. Covalent bond bond formed by directed valence electron clouds. Neutral ... ... Wikipedia
Chemical bonding is the phenomenon of the interaction of atoms, due to the overlap of electron clouds, binding particles, which is accompanied by a decrease in the total energy of the system. The term "chemical structure" was first introduced by A. M. Butlerov in 1861 ... ... Wikipedia
