Nucleophilic reactivity atom size effect

The failure of the heavier donor atoms to follow the same pattern as the lighter ones must be largely an atom size effect. The diffuse orbital of an iodide ion will not overlap well with that of a proton, at least in comparison to that of fluoride ion. As for nucleophilic reactivity, the relative reactivity of F-and 1 will be substrate-dependent. If covalent bonding in the transition state is large, and if the accepting orbital of the electrophile is diffuse, then I will do very well. Alkyl halides are usually in this category. 

It should be noted that the type of cathode reaction has no direct effect on its surface chemistry. The most important aspects are the redox potentials, the particle size, and the level of reactivity of the surface oxygen atoms. Another important aspect relates to the ease of transition metal ion dissolution from the cathode material to the solution phase. In general, as the redox potential is lower, the cathode material is less reactive with the solution species. However, the redox potential is not the main important factor. The nucleophilicity and basicity of the oxygen atoms of the cathode compounds are also highly important. Li MOy compounds are much more basic and nucleophilic than LiMP04 compounds [13]. The phosphorous atoms at the 5+ oxidation state in the olivine compounds moderate the basic nature of the oxygen atoms. Thereby, olivine compounds are much less reactive to solution species than LLMOy compounds [ 14]. Consequently, they can be used as nanoparticles, which help to overcome their poor transport properties. The fluorine atoms in FeFs and its reduction product, LiF, are neither basic nor nucleophilic, and thereby this cathode material does not develop surface chemisfiy in conventional electrol)de solutions. Finally, as the particle size of cathode materials is smaller, they are supposed to be more surface reactive. 

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