The Continuous Range of Bonding Types

Polar covalent bonds may be thought of as intermediate between pure (nonpolar) covalent bonds and pure ionic bonds. In fact, bond polarity is sometimes described in terms oipartial ionic character. This usually increases with increasing difference in electronegativity between bonded atoms. Calculations based on the measured dipole moment of gaseous HCl indicate about 17% ionic character.  

Almost all bonds have both ionic and covalent character. By experimental means, a given type of bond usually can be identified as being closer to one or the other extreme type. We find it useful and convenient to use the labels for the major classes of bonds to describe simple substances, keeping in mind that they represent ranges of behavior. 

Above all, we must recognize that any classification of a compound that we might suggest based on electronic properties musthe consistent with the physical properties of ionic and covalent substances described at the beginning of the chapter. For instance, HCl has a rather large electronegativity difference (0.9), and its aqueous solutions conduct electricity. But we know that we cannot view it as an ionic compound because it is a gas, and not a solid, at room temperature. Liquid HCl is a nonconductor. 

In summary, we can describe chemical bonding as a continuum that maybe represented as 

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Lewis Formulas for Molecules and Polyatomic Ions 7-5 The Octet Rule 7-10 The Continuous Range of Bonding Types... 

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