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

What is the Effective Atomic Number $(EAN)$ of $Cu$ in $[Cu(NH_3)_4]^{2+}$?

Among $V(CO)_6$,$Cr(CO)_5$,$Cu(CO)_3$,$Mn(CO)_5$,$Fe(CO)_5$,$[Co(CO)_3]^{3-}$,$[Cr(CO)_4]^{4-}$,and $Ir(CO)_3$,the total number of species isoelectronic with $Ni(CO)_4$ is. . . . . [Given atomic number : $V=23$,$Cr=24$,$Mn=25$,$Fe=26$,$Co=27$,$Ni=28$,$Cu=29$,$Ir=77$ ]

The effective atomic number $(EAN)$ of cobalt in the complex $[Co(NH_3)_6]^{3+}$ is

The $EAN$ of iron in potassium ferricyanide is

Which of the following complex compounds/ions obeys the Sidgwick $EAN$ rule?