General reactivity and stereochemistry

Fluorine is the most reactive of all elements. It forms compounds, under appropriate conditions, with every other element in the periodic table except He, Ar and Ne, frequently combining 

The tendency for F2 to give F ions in solution is also much greater than for the other halogens as indicated by the steady decrease in oxidation potential (E°) for the reaction X2(soln) -I-2e 2X (aq)  

The corresponding free energy changes can be calculated from the relation AG = —nE°F where n =2 and F = 96.485kJ mol . Note that °(F2/2F ) is greater than the decomposition potential for water (p. 629). Note also the different sequence of values for °(X2/2X ) and for the electron affinities of X(g) (p. 800). A similar anomaly was observed (p. 75) for E° ( J ILa) and the ionization energy of Li(g), and 

The stereochemistry of the halogens in their various compounds is summarized in Table 17.8 and will be elucidated in more detail in subsequent sections. 

Reactivity is enhanced in conditions which promote the generation of halogen atoms, though this does not imply that all reactions proceed via the intermediacy of X atoms. The reversible thermal dissociation of gaseous I2 v 21 was 

2 Linear Nb4F2o C1F2- Br3 , (MeCN)2Br2 I3-, ICI2-, 

4 Tetrahedral CaF2 (fluorite) SrCl2 (fluorite), Br04 , FBr03, IO4- 

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