$(a)$ Answer the following questions :
$(i)$ Which element of the first transition series has highest second ionisation enthalpy ?
$(ii)$ Which element of the first transition series has highest third ionisation enthalpy ?
$(iii)$ Which element of the first transition series has lowest enthalpy of atomisation ?
$(b)$ Identify the metal and justify your answer.
$(i)$ Carbonyl $M(CO)_5$ $(ii)$ $MO_3F$
$(a)$ $(i)$ $\mathrm{Cu} .$ In $\mathrm{Cu}$ the second electron is to be removed from $3 d^{10}$ configuration which is highly stable.
$(ii)$ $\mathrm{Zn}$. The third electron is to be removed from $d^{10}$ configuration which is highly stable.
$(iii)$ $Zn$. Zinc has all electrons paired and hence it cannot form metallic bonds.
(b) (i) $\mathrm{Fe}(\mathrm{CO})_{5}$ As per Effective Atomic Number (EAN) rule.
EAN $=Z$ - [Number of electrons lost to form metalion] + [Number of electrons gained from donor atom]
$\therefore$ EAN $=26-0+(5 \times 2)=36$
$(ii)$ $\mathrm{MnO}_{3} \mathrm{~F}: \mathrm{Mn}$ shows $(+7)$ oxidation state.
In which of the following metallic bond is strongest
When $KMnO_4$ solution is added to hot oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time. This is because
The magnetic moment of a metal ion of first transition series is $2.83 $ $BM$. Therefore it will have unpaired electrons
Mark the variety of iron which has highest melting point
Which one of the following when dissolved in water gives coloured solution in nitrogen atmosphere?