The Group VII Elements F, Cl, Br, I, At

Ele- ment Electronic structure Ion- ization poten- tial (cV) Electron affinity0 (kl g-atom-1 (298°) Dissocia- tion ) energy (kJ mol-1) B.p. C C) M.p. rc) Crys- Cota 1 valent radius, radius, X (Ar X (A)  

The coordination number of the halides in the — 1 state is normally only one, but, in certain metal compounds, bridging halides can be obtained (see page 468) where the coordination number is 2 and in some metal atom cluster compounds (see page 547) triply bridging halide ions with coordination number 3 are found. 

For fluorine there is little evidence for positive behavior, even formally, except perhaps in the ion FC12 in oxygen fluorides the F atom is probably somewhat negative with respect to oxygen, while, in C1F, evidence from chlorine nuclear quadrupole coupling shows that the actual charge distribution involves partial positive charge on Cl. 

Even for the heaviest member of the group, astatine, there is little evidence for any extensive metallic behavior. 

Fluorine occurs widely in Nature, notably as fluorspar, CaF2 cryolite, Na3AlF6 and fluorapatite, 3Ca3(P04)2Ca(F,Cl)2. It is more abundant (0.065%) than chlorine (0.055%) in the earth s crust. 

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Group VII (halogens) are the elements F, Cl, Br, I, and At. Their outer electron configuration is s2p5. 

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