The $EAN$ of $Ni$ in $[Ni(CO)_4]$ is ....

The $EAN$ of iron in potassium ferricyanide is

Which complex follows the Sidgwick $EAN$ rule (where atomic number of $M = 24$)?

$a$. 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 $M(CO)_5$
$ii$. $MO_3F$

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

Which of the following complexes does $NOT$ obey the $EAN$ rule?