Ionization can be divided into chemical ionization and physical ionization.[1]Chemical ionization refers toelectrolyteIn the water solution or molten state, the dissociation zone is oppositechargeAnd move ions freely.There are complete ionization and incomplete ionization in aqueous solution,Strong electrolyteFully ionized in aqueous solution,Weak electrolyteIncomplete ionization occurs in aqueous solution.Ionization is different from electrolysis. The ionization process does not need to be electrified. Electrolysis is a process in which the anion and cation in the electrolyte solution move to the two poles and oxidation-reduction reaction occurs after electrification. In this sense, ionization is the premise and condition of electrolysis.[2]Physical ionization refers to the process in which uncharged particles become charged particles under the action of high-voltage arcs or high-energy rays.[1]
electrolyteThe process of dissociation into oppositely charged ions and free movement of ions in an aqueous solution or in a molten state,[2]Or the process of uncharged particles becoming charged particles under the action of high-voltage arc or high-energy rays.[1]
Arrhenius' ionization theory
Announce
edit
Water electrolysis experiment and research on electrolysis and conductivity began in 1880.In 1884, Faraday first used terms such as "electrolyte" and "ion" in his article "Experimental Research on Electricity".At that time, it was generally believed that the electrolyte would be decomposed into positive and negative ions only when the electrolytic voltage was applied.From 1884 to 1887, Swedish chemist Arrhenius successively published relevant theories.In the article "On the Dissociation of Solute in Water", the basic viewpoints of ionization theory were expounded: (1) Due to the role of solvent, the electrolyte automatically dissociates into positive and negative ions with opposite charges in water.(2) Each electrolyte in an aqueous solution is composed of two parts (in an electrolytic and chemical sense): dissociated molecules and undissociated molecules. The latter continue to dissociate when diluted, so that only dissociated molecules exist in the infinitely diluted solution.The publication of this paper marks the formal establishment of ionization theory.Arrhenius ionization theoryIt has become an important bridge between physics and chemistry, promoted the determination and development of physical chemistry, and opened a new page for the development of the whole chemistry.[2]
Related concepts
Announce
edit
electrolyte
Compounds that can be dissociated into cations and anions in aqueous solution or molten state and conduct electricity are called electrolytes.Such as acid, alkali, salt, active metal oxideperoxide, hydride, etc.Compounds that cannot conduct electricity in aqueous solution or molten state are calledNon electrolyte。The difference between electrolytes and non electrolytes is whether they can conduct electricity when dissolved in water or in molten state.[2]
Ionic compoundAnd some polarCovalent compoundIn the aqueous solution, all ions are ionized into ions without molecules. Such electrolytes belong toStrong electrolyte。Strong acids, bases and most salts are strong electrolytes.Weak acids, weak bases, water and other compounds are partially ionized into ions in aqueous solution, and there is an ionization balance between electrolyte molecules and ionsWeak electrolyte。Whether electrolyte can be completely ionized in solvent is the basis to distinguish strong electrolyte from weak electrolyte.[2]
Ionization equilibrium
ionization
At a certain temperature, when the rate of ionization of weak electrolyte molecules into ions is equal to the rate of ion recombination into molecules in weak electrolyte solution, the state that the concentration of weak electrolyte molecules and ions will not change is called weak electrolyte ionization equilibrium.[2]
Picture Quoted From[2]。
Ionization degree
At a certain temperature, in a weak electrolyte solution of a certain concentration, when the weak electrolyte reaches ionization equilibrium, the percentage of the ionized electrolyte molecules in the original total number of molecules is called the ionization degree of the electrolyte, expressed in α.Generally speaking, under the same conditions, the stronger the electrolyte, the greater the degree of ionization. Therefore, the relative strength of weak electrolyte can be expressed quantitatively by the degree of ionization.[2]
Ionization constant
At a certain temperature, when the ionization of a weak electrolyte reaches equilibrium, the ratio of the product of the ionized ion concentration and the non ionized molecular concentration is called theIonization equilibrium constant, also called ionization constant or dissociation constant, Kiexpress.[2]
classification
Announce
edit
Ionization can be divided into chemical ionization and physical ionization.[1]
Chemical ionization
Chemical ionization refers to the process of electrolytes ionizing into freely movable ions under certain conditions (such as dissolving in some solvents, heating and melting, etc.).Before ionization, there may be no ions (such as hydrogen chloride), or there may be ions, but the ions inside cannot move freely (such as sodium chloride solid).[1]
Chemical ionization can be divided into complete ionization and incomplete ionization (partial ionization).For example, acid is ionized in aqueous solution to formHydrous hydrogen ionAnd acid radical ions.Strong acids are completely ionized, and weak acids are partially ionized.In weak acid solution, there is always a balance between the weak acid molecules that are not ionized and the ionized hydrogen ions and acid radical ions.[2]
Physical ionization
Physical ionization refers to the process in which uncharged particles become charged particles under the action of high-voltage arcs or high-energy rays.This is the case for particles in the ionosphere in the Earth's atmosphere, for example.The particles in the ionosphere are ionized into charged particles under the action of high-energy rays in the universe.The modes of physical ionization include high temperature, electric field and high-energy radiation.[1]
Ionization energy of elements
Announce
edit
In the normal state, the atom is at the lowest level, and then the electron moves in the orbit closest to the nucleus. This state is called the ground state.The energy required for a gaseous atom of an element in the ground state to lose an electron to form a+1 valence gaseous cation is called the first ionization energy of this elementoneexpress.The energy required to make a+1 valence gaseous cation of an element lose an electron to form a+2 valence gaseous cation is called the second ionization energy of this elementtwoexpress.By analogy, there are also the third ionization energy and the fourth ionization energy of elements. Generally speaking, the ionization energy refers to the first ionization energy.The size of ionization energy can be used to measure the difficulty of electron loss of atoms of elements. The smaller the ionization energy, the easier the electron loss, and the stronger the metallicity.Generally, with the increase of the number of electrons lost by atoms in the same element, it is more and more difficult to lose electrons, so the ionization energies of all levels of the same element increase in turn.[5]
ionizing radiation
Announce
edit
ionizing radiationIt refers to the radiation that can directly or indirectly cause the ionization of material atoms. It is a kind of energy released when atoms are transmitted in the form of electromagnetic waves or particles.As early as November 1895, Roentgen, a German physicist, discovered an invisible but penetrating ray, called X-ray, which was applied in medicine shortly after its discovery.In March 1896, French scientist Becquerel found that uranium can emit an invisible and penetrating radiation, which can ionize the air and sensitize the film.In July 1898, the Curies first moved fromPitchblendeIn December of the same year, another new element radium (Ra) was successfully separated and a new term "radioactivity" was put forward.In the early period of nuclear development, the radiation sources used for research and application were mainly radioactive substances from nature, such asGamma ray sourceRadium, radium beryllium mixture that can be made into neutron source, etc., and are usually packaged in small containers to achieve the purpose of safe use and convenient operation.Since then, with the development of nuclear reactors, artificial radionuclides have emerged, and the types and applications of radiation sources have become increasingly diverse, and the use has also increased.At present, nuclear technology has been widely used in national defense, scientific research, industry, agriculture, medicine, communications, transportation, environmental protection, resource development and scientific research, and has played an irreplaceable role in promoting human civilization.[4]
