Question

Effective Atomic Number (EAN) Rule for predicting stability of a coordunation compound (sidwig theory)

Answer 1

Hi Selly,

EAN= at. NO. of metal atom-Electrons lost in ion formation +Electrons gained by coordination.A stable complex complex is formed if EAN is equal to the atomic number of ht next noble gas .for example ,EAN of Fe in [Fe(CN)_{6}]^4-=26-2+6X2=36,i.e.[Kr[ and [Fe(CN)_6]-³,EAN=26-3+6X2=35. Hence ,[Fe(CN)_4]^-4 is more stable
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Answer 2

hi sara ,
Apply the concept of EAN rule on the complexes [Fe(CN)6]4− and [Fe(CN)6]3−.  [Atomic number of Fe = 26].

Let us take the case [Fe(CN)6]4−
Oxidation state of Fe in [Fe(CN)6]4− = +2
No. of electrons in iron = 26
∴ No. of electrons in Fe(II) of the complex = 26−2 = 24
Number of electrons donated by six CN− ligands = 6×2 = 12
∴ EAN of Fe(II) in [Fe(CN)6]4− = 24+12 = 36

Since, this number (36) = number of electrons in the atom of the nearest noble gas (Kr), the complex [Fe(CN)6]4− follows the EAN rule or the EAN rule is valid on this complex

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