An element of the ${\mathrm{I}}^{\mathrm{st}}$ transition series ${\mathrm{X}}^{+3}$ have the highest magnetic moment in series and ${\mathrm{X}}^{+2}$ have non-magnetic nature as low spin complex. If Atomic number of $\mathrm{X}$ is $\mathrm{a}$ and the number of unpaired ${\mathrm{e}}^{-}$ in free state ${\mathrm{X}}^{+2}$ and ${\mathrm{X}}^{+3}$ is $\mathrm{b}$ and $\mathrm{c}$, calculate $\mathrm{a}+\mathrm{b}+2\mathrm{c}$.

Chromite ore is processed through the following sequence:

In this sequence, how many species (from $\mathrm{A}$ to $\mathrm{H}$) show green colour?

The colour of the transition metal ions is/are due to:

Pyrolusite is ${\mathrm{MnO}}_2$ used to prepare ${\mathrm{KMnO}}_4$, ${\mathrm{MnO}}_2\stackrel{\mathrm{I}}{⟶}{\mathrm{MnO}}_2^{2-}\stackrel{\mathrm{II}}{\to }{\mathrm{MnO}}_4^{-}$.

Steps $\mathrm{I}$ and $\mathrm{II}$ are respectively: