The atomic number of cobalt is $27$. The $EAN$ of cobalt in $Na_{3}[Co(NO_{2})_{4} Cl_{2}]$ is

Which of the following coordination complexes is an exception to the $EAN$ rule? (Given atomic numbers: $Pt = 78, Fe = 26, Zn = 30, Cu = 29$)

Find the $EAN$ of $Zn$ in $[Zn(NH_3)_4]^{2+}$?

What is the $EAN$ of $Fe$ in $[Fe(CN)_6]^{3-}$?

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

$[Co(NH_3)_x]Cl_3$ has $EAN$ of $Co=36$. What is the value of '$x$' $:-$