What is the $EAN$ (Effective Atomic Number) of the metal ion in the hexacyanoferrate$(II)$ ion?

Which of the following pairs is not correctly matched?

Which of the following follows the $EAN$ rule?

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

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

The effective atomic number $(EAN)$ of iron in the brown ring complex is: