Question

Which of the following complexes does not obey the EAN rule?

• A. $[PtC{l}_6{]}^{2-}$
• B. $[Co(N{H}_3{)}_6{]}^{3+}$
• C. $[Fe(CN{)}_6{]}^{3-}$
• D. $[Cu(CN{)}_4{]}^{3-}$

Answer 1

Answer: (C)

EAN rule means that the effective atomic number of the central metal must be equal to the atomic number of next noble gas.
For $[Fe(CN{)}_6{]}^{3-}$, Fe is in +3 oxidation state.
EAN $=26-3+(6\times 2)=35$
35 is not equal to the atomic number of the next noble gas Kr (36).