(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 states. (iii) Complete the following equation: MnO_4^(-) + 8H^(+) + 5e^(-) to (iv) Out of Mn^(3+) and Cr^(3+), which is more paramagnetic and why? (Atomic nos.: Mn = 25, Cr = 24)

(i) With reference to structural variability and chemical reactivity,

1.	(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 states. (iii) Complete the following equation: MnO_4^(-) + 8H^(+) + 5e^(-) to (iv) Out of Mn^(3+) and Cr^(3+), which is more paramagnetic and why? (Atomic nos.: Mn = 25, Cr = 24)
Answer» SOLUTION : (ii) Cerium `(CE^(4+))` (III) `MnO_4^(-) +8H^(+) +5e^(-) to Mn^(2+) + 4H_2O` (iv) `Mn^(3+)` is more paramgnetic. Because `Mn^(3+)` has 4 UNPAIRED electrons `(3d^4)` therefore more paramagnetic whereas `Cr^(3+)` has 3 unpaired electrons `(3d^5). `