Question

Which of the following does not follow the EAN rule?
A. \[V(C{{O}_{6}})\]
B. \[Cr(C{{O}_{6}})\]
C. \[Ni(C{{O}_{4}})\]
D. \[W(C{{O}_{6}})\]

Answer 1

Hint: Here for checking EAN rules we have to find an effective atomic number. Then we will check that the effective atomic number is equal to the atomic number of any gas or not?

Step by step solution:
EAN rule, that in a number of metal complexes the metal atom tends to surround itself with sufficient ligands that the resulting effective atomic number is numerically equal to the atomic number of the noble-gas element of the same period. 
\[V(C{{O}_{6}})\]: In this complex compound V contributes 23 electrons and by each covalent bond with CO two electrons are getting shared. So, the total number of electrons is 35 which is not equal to the atomic number of any noble gas.
\[Cr(C{{O}_{6}})\]: In this complex compound Cr contributes 24 electrons and by each covalent bond with CO two electrons are getting shared. So, the total number of electrons is 36 which is equal to the atomic number of “Kr” noble gas.
\[Ni(C{{O}_{4}})\]: In this complex compound Ni contributes 28 electrons and by each covalent bond with CO two electrons are getting shared. So, the total number of electrons is 36 which is equal to the atomic number of “Kr” noble gas.
\[W(C{{O}_{6}})\]: In this complex compound W contributes 74 electrons and by each covalent bond with CO two electrons are getting shared. So, the total number of electrons is 86 which is equal to the atomic number of “Rn” noble gas.
So, from the above explanation the correct answer is “A”.

Note: Here you have to calculate total number electrons carefully, that how many electrons are getting shared by ligands and which metal have how many electrons.