關於ion既問題..chem勁人入黎

1. copper沒有copper(III), 只有copper(I) 和copper (II)

shall I use English to explain?
2. Copper is a transition metal because It has available d-orbitals in both metal form and ion forms. Therefore It has low successive ionization enthalphy. Copper has
[Ar]3d104s1 structure, in order to get a fully-filled d-orbital, Copper has to lose its 4s orbital in order to obtain extra stability. So, Copper (I) is formed.
However, Copper (1) compounds are unstable in aqueous forms but they are quite stable in solid form. It is because, when copper(I) dissolves in water, it involves a hydration process, this process is highly exothermic. Since the energy envolved in this process is sufficient to cause the second ionization energy of copper, (hydration energy> second ionization energy) so disproportionation will occur,
2Cu+ ----> Cu2+ + Cu
copper (I) will disproportionate to copper (II) and copper. So copper (II) is formed.

3. there is no copper (III) in the world. Because Cu(III) is energetically unstable
(no fully-filled d-orbital and s-orbital). Also, the third ionization enthalphy is higher than the hydration enthalphy of Cu(II) or Cu(I), the energy envolved is
not enough to ionize the third outermost electron of Copper


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2008-05-05 18:36:47 補充：
line 9:
Since the energy envolved in this process is sufficient to ionize the second valence electron of copper

In 3:
the energy envolved in the hydration process is not sufficient to ionize the third valence electron of copper

2008-05-05 18:36:56 補充：
1:
Due to the low successive ionization energy, copper can ionize some electrons reasonably (but not all)