Mark the steel in which carbon $\%$  is highest

For the ions $Zn ^{2+}, \,Ni ^{2+}$ and $Cr ^{3+}$ which among the following statements is correct ?

(Atomic number of $Zn =30,\,Ni =28$ and $Cr =24$ )

Essential constituent of an amalgam is

For $M ^{2+} / M$ and $M ^{3+} / M ^{2+}$ systems, the ${E^\Theta }$ values for some metals are as follows:

$Cr ^{2+} / Cr \,-0.9 \,V$

$Cr ^{3} / Cr ^{2+}\,-0.4 \,V$

$Mn ^{2+} / Mn \,-1.2\, V$

$Mn ^{3+} / Mn ^{2+}\,+1.5 \,V$

$Fe ^{2+} / Fe\, -0.4 \,V$

$Fe ^{3+} / Fe ^{2+}\,+0.8\, V$

Use this data to comment upon:

$(i)$ The stability of $Fe ^{3+}$ in acid solution as compared to that of $Cr ^{3+}$ or $Mn ^{3+}$ and

$(ii)$ The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

$(a)$ 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 $M(CO)_5$  $(ii)$  $MO_3F$

In the following members of transition elements, the lowest ionization energy is of