The atomic number of the central metal atom can be determined by the EAN rule.
Given : metal carbonyl is M(CO)x where, M = metal x = 4
Thus, the metal carbonyl is M(CO)4The CO is a neutral ligand, having a lone pair of electrons.
It is a monodentate ligand.
Thus, electrons donated per ligand per donor atom = 2 Number of electrons donated by 4 CO molecule = 2 × 4 = 8 electrons.
According to the EAN rule, the ligands in the coordination sphere of a transition metal complex must provide the necessary number of electrons that will give the central metal ion the electronic configuration of a noble gas.
We know that,Effective atomic number (EAN) for M = Atomic number of M (Z) + Number of electrons donated by 4COLet EAN be 36 (Atomic number of krypton, a rare gas).
36 = Z + 8Z = 36 - 8 = 28
Therefore,Atomic number of M = 28
Hence, the correct option is (D).
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)