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The vigorous reaction between the elements sodium and chlorine forms the white, crystalline compound sodium chloride, common table salt, which contains sodium cations and chloride anions ( Figure 7.2). Chlorine atoms form chlorine gas, Cl 2, a yellow-green gas that is extremely corrosive to most metals and very poisonous to animals and plants. Sodium atoms form sodium metal, a soft, silvery-white metal that burns vigorously in air and reacts explosively with water. Neutral atoms and their associated ions have very different physical and chemical properties.

Once dissolved or melted, ionic compounds are excellent conductors of electricity and heat because the ions can move about freely. Most ionic solids, however, dissolve readily in water. Ionic solids are also poor conductors of electricity for the same reason-the strength of ionic bonds prevents ions from moving freely in the solid state. Ionic solids exhibit a crystalline structure and tend to be rigid and brittle they also tend to have high melting and boiling points, which suggests that ionic bonds are very strong. The properties of ionic compounds shed some light on the nature of ionic bonds. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell.Ĭompounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions. Predict the charge of common metallic and nonmetallic elements, and write their electron configurationsĪs you have learned, ions are atoms or molecules bearing an electrical charge.Explain the formation of cations, anions, and ionic compounds.By the end of this section, you will be able to: