Ionic bonds pass through two or moreatomOr chemical groups lose or gain electrons and become ions.Between oppositely charged ionsstatic electricityWhen two ions with opposite charges are close to each other, they attract each otherNucleusThere is electrostatic repulsion with atomic nucleus. When electrostatic attraction and electrostatic repulsion reach balance, ionic bond will be formed.Therefore, ionic bond refers toanion，cationIntercrossstatic electricityAction formedChemical bond.
Ionic bond belongs toChemical bond, most salts, consisting of alkali metals oralkaline-earth metalFormed bond, activemetallic oxideAll have ionic bonds.Compounds containing ionic bonds are calledIonic compound。The ionic bond is related to the boiling point and hardness of the object.
Ionic bond, also known as salt bond, isChemical bondOne of two or moreatomorChemical groupLoss or gainElectronicsAnd becomeIonsLater.Band reversalchargeExists between atoms or groups ofstatic electricityAttraction, when two atoms or groups with opposite charges are closeWater moleculeIs released into free water withnegative electricityAnd bandpositive electricityThe electrostatic attraction between atoms or groups in order to form ionic bonds.
Such chemical bonds are oftenMetalAndNonmetalIntermittent formation.Those who lose electrons are oftenMetalThe atom of the element, and the electron is often obtained byNonmetalThe atom of the element.With oppositechargeDue to the electromagnetic force, the ions of.Ionic bond ratiohydrogen bondStrong, its strength is the same ascovalent bondApproach.
Bonding particles: anions and cations[1]；
Nature of bond: between anion and cationElectrostatic effect;
Influencing factors: the larger the radius of anion and cation, the smaller the ionic bond;What is the charge of anion and cation[2]；
Electronic formula: the formula that uses "·" or "×" around the element symbol to represent the outermost electron of the atom[1]。
nature
The ionic bond has strong force, no saturation and no directivity.
Ionic bonds exist inIonic compoundIonic compounds exist as crystals at room temperature.
Some people may ask whether the charge of anion and cation is neutralized when they are combined?In addition to electrostatic attraction, there are electrons between sodium ion and chloride ion,NucleusRepulsive interaction with atomic nuclei.When the two ions are close to a certain distance, the attraction and repulsion reach a balance, and a stable relationship is formed between the anion and cationChemical bond。Therefore, the so-called neutralization of anionic and cationic charges will not occur.
Lattice energy
Ionic bondedBond energyLarge, reflected in ionic compoundsHigh melting boiling pointThe bond energy of ionic bond is calledLattice energySign of lattice energy and dissociation process of ionic crystalsenthalpy changeThe symbols of are consistent[1]。The lattice energy can pass throughBorn Hubble cycle（Bōrn-Haber cycle）OrBorn Rand formula（Bōrn-Landé）It can also be measured by experiment[2]。
The following is through the Born Hubble cycle（Bōrn-Haber cycle）Calculated lattice energy data, unit:Kilojoule/Mo
Ionic bonds are formed by electron transfer (those who lose electrons are cations, those who gain electrons are anions).Between oppositely charged ionsstatic electricityWhen two ions with opposite charges are close to each other, they attract each otherNucleusThere is electrostatic repulsion with the atomic nucleus. When the electrostatic attraction and electrostatic repulsion reach balance, an ionic bond is formed, that is, between positive ions and negative ionsElectrostatic attractionThe chemical bond formed.[1]
Schematic diagram of ionic bond formation
Ions can be single ions, such as Na+、Cl-；Or byAtomic clusterFormation;as
，
Etc.[1]It is often found thatNonmetalIntermittent formation.It is often the atoms of metal elements that lose electrons, while it is the atoms of non-metallic elements that gain electrons.Generally, active metals form ionic bonds with active nonmetals, such as potassium, sodium, calcium and other metals, and chlorine, bromine and other nonmetals can form ionic bonds when they are combined.[1]And the reaction will occur only when the overall energy level drops (atoms connected by chemical bonds have lower energy levels than free atoms).The more the drop, the stronger the bond formed.
In reality, there is no "pure" ionic bond between atoms.All keys have more or lesscovalent bondComponents of.The higher the electric average between bonding atoms, the lower the ionic bond composition.The greater the electronegativity difference between bonding atoms, the greater the polarity of the bond. When the difference is large enough, it can be assumed that the "shared" electrons become the "possessions" of the atoms with greater electronegativity.In other words, electrons are transferred from one atom to another, that is, ionic bonds are formed.
The bonding force of ionic bond is great, so the ionic crystal has high hardness, high strength, small coefficient of thermal expansion, but high brittleness.It is difficult for ionic bonds to generate electrons that can move freely, so ionic crystals are good insulators. However, in the molten or solution state, ionic bonds will ionize, producing free positive and negative ions, which can conduct electricity.In ionic bonding, because the outer electrons of ions are firmly bound, the energy of visible light is generally not enough to excite them, so they do not absorb visible light, so typical ionic crystals are colorless and transparent.AltwoOthree、MgO、TiOtwo, NaCl and other compounds are ionic bonds.[3]
Ionic bond formation
Whenperiodic table of ele mentsWhen the atoms of positive and negative elements far away from each other come into contact with each other, the former loses the outermost valence electron and becomes a positive ion with positive charge, while the latter gains electrons and becomes a full shell negative ion with negative charge.Positive ions and negative ions attract each other by electrostatic attraction;At the same time, when they are very close, repulsion will occur, and the gravitational force and repulsion force will be equalStable ionic bond。
It is believed that atoms in molecules or crystals are not simply stacked together, but have strong interactions.Chemically, the strong force between atoms in such molecules or crystals (sometimes atoms gain or lose electrons and change into ions) is called chemical bond.The essence of a key is a force.So some are also called bond forces, or bonds.
Formed by combining sodium and chlorinationsodium chlorideFor example:
fromatomIn terms of structure, the outermost sodium atomElectronic layerThere is one electron on it, which is easy to lose;The chlorine atom has 7 electrons in the outer electron layer, and it is easy to get one electron.When the sodium atom meets the chlorine atom, the sodium atom loses one of the outermost electrons and becomesSodium ion, withpositive electricityThe chlorine atom gets the electrons lost by sodium and becomes negatively chargedChloride ion, the attraction of the opposite charge of the anion and cation, andNucleusBetweenexcludeThe action reached equilibrium, forming a stable ionic bond.[1]
