The Proton as a Different Sort of Ion

Being such a famous performer, the shape and size of the hydronium ion have been determined by NMR and other methods. The HjO ion has a rather flat trigonal-pyramidal structure with the hydrogen at the comers of the pyramid and the oxygen in the middle, as shown in Fig. 4.118. Its structure resembles that of the ammonia molecule. 

A great deal can be learned about the proton simply by reviewing some energy quantities assigned to it. The energy change associated with the interaction between a 

The value of -401 kJ moF for the hydration energy of the hydronium ion indicates that it itself is hydrated. How many molecules of water hydrate it A look at Fig. 4.119 shows that approximately three water molecules are associated to the hydronium ion, giving a structure of (H904) .  

How is the H a nonconforming ion For one thing, because of its special association with water it is nearly always tightly bound to one water. This structure seems to exist as an entity which itself is being solvated by other waters. 

This is not the only nor the main differentiating property of the nonconforming ion. Having seen that H is usually to be found tightly attached to HjO, one would expect that H30 would be the transporting entity. It is not HjO movement contributes only about 10% of the transport of in aqueous solution, and the main mode of transport is, indeed, entirely different from that of other ions. 

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