Ionic compound

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The crystal structure of sodium chloride, NaCl, a typical ionic compound. The purple spheres are sodium cations, Na+, and the green spheres are chloride anions, Cl.

In chemistry, an ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Usually, the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion. Ions in ionic compounds are held together by the electrostatic forces between oppositely charged bodies. Ionic compounds have high melting and boiling points, and they are hard and very brittle.

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Ions can be single atoms, as the sodium and chlorine in common table salt sodium chloride, or more complex groups such as the carbonate in calcium carbonate. But to be considered an ion, they must carry a positive or negative charge. Thus, in an ionic bond, one 'bonder' must have a positive charge and the other a negative one. By sticking to each other, they resolve, or partially resolve, their separate charge imbalances. Positive to positive and negative to negative ionic bonds do not occur. (For an easily visible analogy, experiment with a pair of bar magnets.)

Chemical compounds are never strictly ionic. Even the most electronegative/electropositive pairs such as caesium fluoride exhibit a degree of covalency. Similarly, covalent compounds often exhibit charge separations. See also HSAB theory.

Ionic compounds have strong electrostatic bonds between particles. As a result, they generally have very high melting and boiling points. They also have good electrical conductivity when molten or in an aqueous solution.[1] Ionic inorganic compounds are solids at room temperature and usually form crystals, they have high melting points, and are soluble in water. Unlike organic compounds they do not char nor ignite. On the other hand organic compounds have low melting points, most of them are insoluble in water, and characteristically they ignite quite easily.Cite error: A <ref> tag is missing the closing </ref> (see the help page).


According to the IUPAC, an ionic compound's common name is written using two words. The name of the cation comes first (with the oxidation number written in parentheses when using Stock nomenclature), followed by the name of the anion.[2] For example, Fe2(SO4)3 is named as iron(III) sulfate. If the Classical naming system is being used, some ionic compounds have special "old" names, such as ferrous and ferric, for iron(II) and iron(III) respectively, and cuprous and cupric, for copper(I) and copper(II) respectively.

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  1. ^ Dutta, Priti. "What are the characteristics of Ionic Compunds". Retrieved 2 December 2012. 
  2. ^ Kotz, John C.; Weaver, Paul M (2006). Chemistry and Chemical Reactivity (Sixth ed.). Belmont, CA: Thomson Brooks/Cole. p. 111. ISBN 0-534-99766-X.