Random Chemistry Practice

(i) With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids. (ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state. (iii) Complete the following equation: $MnO_4^- + 8H^+ + 5e^- \rightarrow$ (iv) Out of $Mn^{3+}$ and $Cr^{3+}$, which is more paramagnetic and why? (Atomic nos. : Mn =25, Cr = 24)