Chlorine relative radii

The relatively small radius of F", 1.19 A, is almost identical with that of the oxide, O2-, ion (1.25 A) consequently, many fluorides and oxides are ionic with similar formulae and crystal structures, for example, CaO and NaF. The compounds of the other halogens with the same formula usually form quite different lattices and may even give molecular lattices. Thus chlorides and other halides often resemble sulfides, just as the fluorides often resemble oxides. In several cases the fluorides are completely ionic, whereas the other halides are covalent for example, CdF2 and SrF2 have the CaF2 lattice (nearly all difluorides have the fluorite or rutile structure), but CdCl2 and MgCl2 have layer lattices with the metal atoms octahedrally surrounded - by chlorine atoms.-----------------------------... 

In a crystal of the substance (chlorine) the molecules are attracted together by their van der Waals interactions and assume equilibrium positions at which the attractive forces are balanced by the characteristic repulsive forces between atoms, resulting from interpenetration of their electron shells. Let us call one-half of the equilibrium internuclear distance between two chlorine atoms in such van der Waals contact, corresponding to the relative positions of two molecules, the van der Waals radius of chlorine. 

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