What is the $EAN$ of $Zn$ in $[Zn(NH_3)_4]^{2+}$?

What is the $EAN$ of nickel in $Ni(CO)_4$?

In which of the following pairs is the $EAN$ of the central metal atom not the same?

The effective atomic number $(EAN)$ of $Co(CO)_4$ is $35$,which makes it less stable. It attains stability by:

What is the value of $n$ in the anionic species $[V(CO)_6]^{n-}$ if it follows the Sidgwick $EAN$ rule and has an octahedral shape?

Select the odd one w.r.t. $EAN$ :-