$EAN$ of the central metal in the complexes $K_2[Ni(CN)_4]$,$[Cu(NH_3)_4]SO_4$ and $K_2[PtCl_6]$ are respectively.

For the complex $Cr(CO)_x$,find the value of $x$?

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

$EAN$ of complex $[Fe(C_2O_4)_3]^{3-}$ is

The $EAN$ of $Mg$ in $[Mg(EDTA)]^{2-}$ is ...

$a$. Answer the following questions:
$i$. Which element of the first transition series has the highest second ionisation enthalpy?
$ii$. Which element of the first transition series has the highest third ionisation enthalpy?
$iii$. Which element of the first transition series has the lowest enthalpy of atomisation?
$b$. Identify the metal and justify your answer:
$i$. Carbonyl $M(CO)_5$
$ii$. $MO_3F$