Ionic compounds are composed ofcationandanionConstituent compounds.When active metals (such as sodium, potassium, calcium, magnesium, etc.) and active nonmetals (such as fluorine, chlorine, oxygen, sulfur, etc.) combine with each other, the active metals lose electrons and form positively charged cations (such as Na+、K+、Ca2+、Mg2+Active nonmetals get electrons to form negatively charged anions (such as F-、Cl-、O2-、S2-Cations and anions form ionic compounds by electrostatic action.For example, sodium chloride is composed of positively charged sodium ion (Na+）And negatively chargedChloride ion（Cl-）Ionic compounds formed by.In ionic compounds, the total number of positive charges carried by cations is equal to the total number of negative charges carried by anions, and the whole compound is electrically neutral.
Ionic compounds are composed ofanion(Anion, with negative charge) andcation(Cation, with positive charge)Coulomb forceOfIonic bondA compound that combines.Ionic compounds usually have high melting points and boiling points, and can conduct electricity when melting or when ionizing the aqueous solution that produces its constituent ions.Most ionic compounds are solid at room temperature, but some exist in liquid ionic compounds at room temperature, which are usually salts containing complex organic components.Note the difference between liquid ionic compounds and ionic compound solutions, which contain some molecules with no electricity.
Ionic compounds are compounds composed of cations and anions.When active metals (such as potassium, calcium, sodium, magnesium, etc.) and active nonmetals (such as fluorine, chlorine, oxygen, sulfur, etc.) combine with each other, the active metals lose electrons and form positively charged cations (such as Na+、K+、Ca2+、Mg2+Active nonmetals get electrons to form negatively charged anions (such as F-、Cl-、O2-、S2-Etc.).
Cations and anions form ionic compounds by electrostatic interaction.For example, sodium chloride is composed of positively charged sodium ion (Na+）And negatively charged chloride ion (Cl-）Ionic compounds formed by.Many alkalis (such as NaOH, KOH, Ba (OH))twoEtc.) and salt (such as CaCltwo、KNOthree、CuSOfour) are ionic compounds.
In ionic compounds, the total number of positive charges carried by cations is equal to the total number of negative charges carried by anions, and the whole compound is electrically neutral.Most ionic compounds cannot conduct electricity in solid (or crystalline) state, while their aqueous solution or molten state can conduct electricity.Generally speaking, ionic compounds have high melting and boiling points, high hardness, brittleness, difficulty in compression and volatilization.
Some alkaline oxides, such as NatwoO、KtwoO. Common salts such as NaCl, KF, and common bases such as NaOH are ionic compounds.
Existing form
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Ionic compounds are present in:
1. Compounds formed between active metals (metal elements of the first and second main groups) and active non-metallic elements (elements of the sixth and seventh main groups)
2、metallic elementAndAcid radical ionCompounds formed between.(Acid ion such as sulfate ion SOfour2-Nitrate ion NOthree-Carbonate ion COthree2-Etc.);
3. Ammonium ion (NHfour+）And acid ion, or between ammonium ion and non-metallic element, such as NHfourCl、NHfourNOthree。
4. NaH, KH and other active metal hydrides.
Ionic compounds areelectrolyte。stayMelting stateIt can conduct electricity (such substances are easy to decompose or oxidize when heated).Some can conduct electricity in water, and some can not (such substances are easy to react with water or insoluble in water).
Function in primary battery: form a closed circuit.
Differentiation of related concepts
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Both ionic compounds and covalent compounds involve the movement of electrons.
Ionic compounds are compounds formed by ionic bonds, which are formed by electron transfer (those who lose electrons are cations, those who gain electrons are anions).It is formed between positive ions and negative ions due to electrostatic effectChemical bond。
Covalent compounds are formed by sharing electronscovalent bondThe covalent bond is a kind of chemical bond formed by combining compounds. Two or more atoms use their outer electrons together to reach the state of electron saturation under ideal conditions, thus forming a relatively stable and solid chemical structure called covalent bond.Unlike ionic bonds, the atoms entering the covalent bond do not show electricity outward because they do not gain or lose electrons.The strength of covalent bond is stronger than that of hydrogen bond, not much different from that of ionic bond or even stronger than that of ionic bond.
Ionic compound
Covalent compound
Constituent particle
Anion and cation
Molecule or atom
Interaction between ions
Ionic bond
Covalent bond between molecules or atoms
Melting boiling point
higher
Generally low, with a few high (such as SiOtwo）
Conductivity
Conduction in molten state or aqueous solution
The molten state is non-conductive. Some are conductive (sulfuric acid) and some are non-conductive (sucrose) when dissolved in water
Breaking force during melting
The ionic bond must be destroyed, and the covalent bond may be destroyed
(such as sodium bicarbonate)
Generally, the covalent bond is not broken, and only a few of them are broken
（SiOtwo）
example
Strong alkali, most salt, active metal oxide or peroxide or superoxide
Acids, non-metallic hydrides, oxides
Judgment method
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(1) Judge according to the properties of the constituent elements of the compound
(2) Judge according to whether the ionic bond of the compound is ionic bond or covalent bond
(3) Judge according to the type of compound
(4) Judge according to the conductivity of the compound
(5) Judge according to the melting and boiling point of the compound
