What is the oxidation state of cobalt in a coordination complex if its $EAN$ is $36$ and the value of $C.N.$ is $6$? (Given: Atomic number of cobalt = $27$).

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

What is the Effective Atomic Number $(EAN)$ of $Co$ in $[Co(NH_3)_6]^{3+}$?

In the brown ring complex,if $NO$ is considered as a neutral ligand,then the $EAN$ would:

The Effective Atomic Number $(EAN)$ of iron in potassium ferricyanide 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 $M(CO)_5$
$ii$. $MO_3F$