The $EAN$ of cobalt is $36$ in $[Co(NH_3)_2O_2(en)Cl]$. Thus,$O_2$ 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 $M(CO)_5$
$ii$. $MO_3F$

Effective Atomic Number $(EAN)$ of $Co$ in $Co_2(CO)_8$ will be

The Effective Atomic Number $(EAN)$ of $Ni$ in $Ni(CO)_4$ is:

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

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