In which of the following ions is $d-d$ transition $NOT$ possible?

Explain giving reasons:
$(i)$ Transition metals and many of their compounds show paramagnetic behaviour.
$(ii)$ The enthalpies of atomisation of the transition metals are high.
$(iii)$ The transition metals generally form coloured compounds.
$(iv)$ Transition metals and their many compounds act as good catalysts.

The common positive oxidation states for an element with atomic number $24$ are:

The number of unpaired electrons in $Co^{2+}$ is:

The correct order of $E^o$ $M^{2+}/M$ values with negative sign for the four successive elements $Cr$,$Mn$,$Fe$ and $Co$ is

The general electronic configuration of transition elements is