What is ion in physics. General and inorganic chemistry. Mechanism of the formation of ions
Iona ions
(from Greek. Iōn - coming), charged particles formed from atom (molecules) as a result of loss or addition of one or more electrons. In solutions, positively charged ions are called cations, negatively charged ions - anions. The term is proposed by M. Faraday in 1834.
IonsIons (from Greek. Ion - going), electrically charged particles formed as a result of the loss or attachment of one or more electrons (cm. Electron (particle)) (or other charged particles) to the atom, molecule, radical or other ion. Positively charged ions are called cations (cm. CATION), negatively charged ions - anions (cm. ANION). The term is proposed by M. Faraday (cm. Faraday Michael) In 1834
Ions are denoted by a chemical symbol with an index located at the top of the right. The index indicates the sign and value of the charge, i.e., the multiplicity of the ion, in the unit charge units. With a loss or acquisition by atom 1, 2, 3 ... electrons are formed, respectively, one-, two and three-chain ions (see ionization (cm. IONIZATION)), for example Na +, Ca 2+, Al 3+, Cl -, SO 4 2-.
Atomic ions are also denoted by a chemical symbol of an element with Roman numbers indicating the multiplicity of ion, in this case the Roman numbers are spectroscopic characters and their value is greater than the charge value per unit, i.e. Ni means a neutral atom n, the designation of the NII ion means once charged ion n +, Niii means N 2+.
The sequence of ions of various chemical elements containing the same number of electrons forms an isoelectric row.
Ions can enter into molecules of substances, forming molecules due to ion connection (cm. Ion connection). In the form of independent particles, in an unbound state, the ions are found in all aggregate states of the substance - in gases (in particular, in the atmosphere), in liquids (in melts and solutions), in crystals. In liquids, depending on the nature of the solvent and the dissolved substance, the ions may exist infinitely for example, for example, the Na + ion in the aqueous solution of the table salt NaCl. Solids in solid state usually form ionic crystals (cm. Ionic crystals). The crystal lattice of metals consists of positively charged ions, inside which is "electronic gas". The energy of the interaction of atomic ions can be calculated using various approximate methods that take into account interatomic interaction (cm. Interatomic interaction).
The formation of ions occurs in the process of ionization. To remove an electron from a neutral atom or molecule, it is necessary to spend certain energy, which is called ionization energy. The energy of ionization attributed to the charge of the electron is called ionization potential. The affinity for the electron is the characteristic opposite of the ionization energy, and shows the amount of the bond energy of the additional electron in the negative ion.
Neutral atoms and molecules are ionized under the action of optical radiation quanta, X-ray and G-radiation, electric field when colliding with other atoms, particles, etc.
In the gases of ions are formed mainly under the action of blows of large energy particles or when photonyondition under the action of ultraviolet, X-ray and G-rays (see ionizing radiation (cm. Ionizing radiation)). Formed by ions in ordinary conditions are short-lived under normal conditions. At high temperature, the ionization of atoms and ions (thermal ionization, i.e. thermal dissociation with the electron separation) can also occur as an equilibrium process (cm. Equilibrium)in which the degree of ionization increases with an increase in temperature and with a decrease in pressure. Gas moves to the plasma state (cm. PLASMA).
Gas ions play a major role in many phenomena. In natural conditions, ions are formed in the air under the action of cosmic rays, solar radiation or electric discharge (zipper). The presence of ions, their form and concentration affect many physical properties of air, on its physiological activity.
encyclopedic Dictionary. 2009 .
Watch what is "ions" in other dictionaries:
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Ions, electrically charged particles resulting from an atom (molecule) as a result of loss or addition of one or more electrons. Positively charged ions are called cations, negatively charged ions anions ... Modern encyclopedia
ions - - electrically charged atoms or molecules. General Chemistry: Tutorial / A.V. John ions - electrically charged particles arising from the loss or addition of electrons atoms, molecules and radicals. Dictionary on analytical chemistry ... ... Chemical terms
Dispatch products of any body with electrolysis. A dictionary of foreign words included in the Russian language. Chudinov A.N., 1910 ... Dictionary of foreign words of the Russian language
Ion (Greek. Όόν "Going") an electrically charged particle (atom, molecule) formed, usually, as a result of loss or addition of one or more electrons atoms or molecules. Charge of ion Katten charge electron. Concept and ... ... Wikipedia
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- (from Greek. ión running) electrically charged particles formed by loss or addition of electrons (or other charged particles) atoms or groups of atoms. Such groups of atoms can be molecules, radicals or others, I. ... ... Great Soviet Encyclopedia
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And he It is an electrically charged particle. At the same time, the ion can have both a positive electrical charge and negative. In the first case, it is called the cation, and in the second - anion.
The ion may be an atom, molecule or a free radical, if, of course, they have any charge. By the way, the charge of the ion can not be infinitely small, and the particle he is represented is elementary.
Ions are also chemically active particles, so they can react as with other particles (not charged) and among themselves.
Iona, like independent particles, are found almost everywhere. They are in the atmosphere, in various liquids, in solids and even in the interstellar space, where the air or some substance in principle is extremely small.
History
For the first time, the concept of "ion" introduced the famous scientist Michael Faraday in 1834. Studying the spread of electricity in various media, it suggested that the electrical conductivity of some of them can be caused by the presence in these media and substances of certain electrically charged particles. So he called them by ions. The scientist also introduced the concepts of cations and anions. Since positive ions are moving toward a negatively charged electrode - the cathode, he called them cations. The negative ions are moving on the contrary - to the anode, then they should be called anions.
Multiatomic particles carrying electric charge. The charge of the ion is Katten elementary electrical charge and always integer. The charge of the one-nominal ion of the chemical element in the number and sign coincides with the degree of oxidation of this element; The charge of the polyhydric ion is equal to the algebraic amount of the degrees of the oxidation of the elements, taking into account the number of their atoms. Positively charged ions (for example, K +, Ca 2+, νη + 4) are called cations (from the Greek κατιών - going down), negatively charged ions (for example, SL -, SO 4 2-, CH 3 SO -) - anions ( From the Greek ανιών - going up). The process of formation of ions is called ionization. The terms "ion", "Kation" and "Anion" introduced in 1834 by M. Faraday, who studied the effect of the electric field on aqueous solutions of various chemical compounds. In a constant electric field, the cations are moved to a negatively charged electrode (cathode), anions - to a positively charged electrode (anode).
In the form of independent particles, the ions may exist in all aggregate states of the substance: in the gases (see ions in gases, ions in the atmosphere), in crystals (see ionic crystals), in plasma, in liquids - in melts (see ionic fluids) and solutions (see electrolytic dissociation). Ions are structural units of chemical compounds with ion chemical bond. Such compounds in solid state, melts and solutions consist of cations and anions; For example, sodium chloride NaCl is from Na + cations and CL-anions, potassium acetate CH 3 COPs - from K + Cations and CH3SOO Cations -. Some compounds with polar covalent bond (for example, HCL chloride) when dissolved in water and other polar solvents dissociate into ions. Depending on the nature of the solvent and the dissolved substance contained in the solutions of ions, they can either interact with solvent molecules, as a result of which solvate shells are formed around the ions, or it is quite close, forming ionic pairs.
The ions are formed during the separation of electrons from atoms and molecules in the gas phase (at the same time the ionization energy is consumed), or as a result of the addition of electrons to such atoms and molecules (the energy spent or released, the affinity of the atom or molecule to the electron). The formation of ions also leads to the attachment of a simple composition of the neutral molecule or another ion. For example, when the H + ion is connected to the water molecule H 2 o, ion hydroxonium H 3 O + is obtained. It is possible to form ions in the destruction of molecules as a result of thermal or radiation impact. In the formation of the ion, the total initial charge of particles participating in this process is always preserved (if the ions were formed from neutral atoms or molecules, then the total charge of all ions is zero). Some molecules that are in solutions or crystals, remaining overall electrophetles, contain oppositely charged groups in various areas (see Zwitter ions). A complex consisting of several neutral atoms or molecules and ions is clustered ion.
Chemical reactions in solution (or melt) with the participation of ionic compounds are due to the movement of ions in this medium and the formation of new neutral particles or more complex ions. In living organisms, the ions are involved in various metabolic processes, regulation of muscle contractions, transmission of nerve impulses, etc. (See, for example, in the article ion pumps).
Lit.: Crosses G. A. Thermodynamics of ionic processes in solutions. L., 1984.
And he - single or multiatomic electrically charged particle of a substance resulting from a loss or an atom attachment as part of a molecule of one or more electrons.
Charge of ion Katten charge electron. The concept and term "ion" introduced Michael Faradays in 1834, which, studying the effect of electric current into aqueous solutions of acids, alkalis and salts, suggested that the electrical conductivity of such solutions is due to the movement of ions. Positively charged ions moving in a solution to the negative pole (cathode), Faradays called cations, and negatively charged moving to the positive pole (anode) - anions.
The properties of ions are determined by:
1) the sign and the magnitude of their charge;
2) the structure of ions, i.e. the arrangement of electrons and strength of their connections, and external electrons are especially important;
3) their dimensions determined by the radius of the outer electron orbit.
4) the strength of the electronic shell (deformability of ions).
In the form of independent particles, the ions are found in all aggregate states of the substance: in gases (in particular, in the atmosphere), in liquids (in melts and solutions), in crystals and plasma (in particular, in interstellar space).
Being chemically active particles, ions come into reactions with atoms, molecules and among themselves. The ion solutions are formed as a result of electrolytic dissociation and determine the properties of electrolytes.
The number of elementary electrical charges in ions in solutions almost always coincides with the valence of this atom or group; Gas ions may have another number of elementary charges. Under the influence of sufficiently energetic effects (high temperature, high frequency radiation, high speed electrons), positive ions can be formed with different numbers of electrons, up to bare nuclei. Positive ions are indicated by the sign + (plus) or point (for example, MG ***, AL +++), negative sign - (minus) or a sign "(CL -, BR"). The number of signs denotes the number of excess elementary charges. Most often, ions are formed with resistant external electronic shells corresponding to the shell of noble gases. The ions from which crystals are constructed, and ions encountered in solvents and solvents with high dielectric constants belong mostly to this type, for example, alkaline and alkaline earth metals, haloches, etc., however, and so on. transition ions in which external shells contain from 9 to 17 electrons; These ions can move relatively easily in the ions of another type and value (for example, Fe - -, SI ", etc.).
Chemical and physical properties
The chemical and physical properties of ions are sharply different from the properties of neutral atoms, reminding in many ways the properties of atoms of other elements that also have the number of electrons and the same outer electron shell (for example, the "reminds of AR, F" -NE). Simple ions, as showing the wave mechanics, have a spherical shape. The dimensions of the ions are characterized by the magnitudes of their radii, which can be determined empirically according to the X-ray analysis of crystals (Goldshmidt) or calculated theoretically methods of wave mechanics (Pouulig) or statistics (Fermi). The results obtained by both methods give a completely satisfactory coincidence. A number of properties of crystals and solutions is determined by the radii of the ions from which they consist; In crystals, these properties are the energy of the crystal lattice and largely its type; The solvent solutions are polarized and attract the solvent molecules, forming a variable composition shell, this polarization and strength of the bond between ions and solvent molecules are determined by almost exclusively radii and charges of ions. At all, the effect of the ion field on the solvent molecules, shows the calculations of the zwick, which found that the water molecules are near the ions under pressure of about 50,000 atm. The strength (deformability) of the outer electron shell depends on the degree of associations of external electrons and causes mainly the optical properties of ions (chromaticity, refraction). However, the chromaticity of ions is also associated with the formation of ions of various compounds with solvent molecules. Theoretical calculations of the effects associated with the deformation of electronic shells are more difficult and less endowed than calculating the interaction forces between ions. The reasons for the formation of ions in solutions are not known; The most believable is that the molecules of soluble substances are broken into ions by the solvent molecular zero; Heteropolar, i.e., the crystals constructed from ions give the ions immediately when dissolved. The value of the molecular field of the solvent is confirmed as if the parallelism between the size of the dielectric constant solvent, which is an approximate measure of the voltage of its molecular field, and the degree of dissociation (Nernst-Thomson rule, experimentally confirmed by Walden). However, ionization occurs in substances with small dielectric constants, but here it dissolves mainly electrolytes, giving complex ion. Complexes are sometimes formed from the ions of the soluble substance, sometimes the solvent also takes part in their formation. For substances with small dielectric constants, the formation of complex ions is also characteristic of the addition of non-electrolytes, for example (from 2 H 5) 0VG 3 gives a conductive chloroform when mixed with chloroform
System. The external sign of the formation of complex ions is the so-called. Anomalous electrical conductivity, in which the graph depicting the dependence of the molar conduit from dilution gives a maximum of concentrated solutions and a minimum of further breeding.
The nomenclature according to the chemical nomenclature, the name of the cation consisting of one atom coincides with the name of the element, for example, Na + is called a sodium ion, sometimes added in brackets, for example, the name of the FE 2+ cation is iron (II). The name consists of one anion atom is formed from the root of the Latin name of the element and suffix " -If /id"For example, F - is called fluoride ion.
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