(i)with reference to structural variability and chemical reactivity write the differences between lanthanoids and actinoids
(ii) Mame a member of the lanthanoid series which is well known to exhibit +4 oxidation state
(iii) Complete the following equation :`MnO_(4)^(-)+8H^(+)+5e^(-)rarr`
(iv) out of `Mn^(3+)` and `Cr^(3+)` which is ore paramagnetic and why? Atomic nos : Mn =25 Cr =24

Explanation

(i) Lanthanoids/Acitinoids
(a) They are not radioactive (expect pm ) but they are radioactive
(b) They mainly show `+3` oxidation state. .They can show up to '+7' oxidation state
(c ) Their magnetic nature can be easily explained .But their magnetic nature can not be easily explained .
(d) Their physical and chemical properities have been studied throughly . but their physical and chemical properties have not been studied throughly
(ii) cerium (Ce)
(iii) `MnO_4-+8H+5e-Mn_2++42H_2O`
(iv)`Mn^(+3)=[Ar]` 4 so `3d^(4)(4"unparied") e^(-)Cr^(+3)=[Ar]4 S_(3)d_(3) "unpaired" e^(-))"Mn"^(+3) "has more no of unpaired" e^(-) "has" Cr^(+3) " Hence " Mn^(3+)` is more paramagnetic .