V=3d34s2;V2+=3d3=3 unpaired electrons Cr=3d54s1;Cr2+=3d4=4 unpaired electrons Mn=3d54s2;Mn2+=3d5=5 unpaired electrons Fe=3d64s2;Fe2+=3d6=4 unpaired electrons Hence the correct order of paramagnetic behaviour V2+<Cr2+=Fe2+<Mn2+ (b) For the same oxidation state, the ionic radii generally decreases as the atomic number increases in a particular transition series, hence the order is Mn2+>Fe2+>Co2+>Ni2+ (c) Larger size, least hydrated more stable in aqueous solution. As we move across the period (Sc3+→Cr3+→ Fe3+→Co3+), the ionic size usually decreases. Sc3+ with the large size as least hydrated and hence more stable. (d) Sc−(+2),(+3) Ti−(+2),(+3),(+4) Cr−(+2),(+3),(+4),(+5),(+6) Mn−(+2),(+3),(+4),(+5),(+6),(+7) i.e. Sc<Ti<Cr<Mn