Electronegativity halogen family elements

Most of the halides can be classified into two categories. The flnorides and chlorides of many metallic elements, especially those belonging to the alkali metal and alkaline earth metal (except beryllium) families, are ionic componnds. Most of the halides of nonmetals snch as snlfnr and phosphorus are covalent compounds. As Fignre 4.10 shows, the oxidation nnmbers of the halogens can vary from -1 to +7. The only exception is flnorine. Because it is the most electronegative element, flnorine can have only two oxidation nnmbers, 0 (as in F2) and -1, in its compounds. 

The fact that x(0) and k tend to vary inversely means that atomic properties related to electronegativity may sometimes not change monotonically within a family of elements. A number of examples of this have been observed and discussed [13-16,19-24]. For instance, in a recent computational study of the electrostatic potentials associated with naphthalene derivatives, we found evidence that the electron-attracting tendencies of the halogens in 1-halonaphtha-lenes increase in the order F < Br < Cl [24]. 

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