Explain :
(i) Actinoid contraction is greater from element to element than canthanoid contraction. Why?
(ii) The enthalpies of atomisation of the transsition metals are high. Why?
Complete the reactions :
(i) `Fe^(2+)+MnO_(4)^(-)+8H^(+)rarr`
(ii) `CuO_(4)^(2-)+H^(+)rarr`

Explanation

(i) Due to poor shielding effect of 5f electrons.
(ii) Because of large number of unpaired electrons in their atoms they have stronger interatomic interaction resulting in higher enthalpies of atomisation.
(i) `5Fe^(2+)+MnO_(4)^(-)+8H^(+)rarrMn^(2+)+5Fe^(3+)+4H_(2)O`
(ii) `2CrO_(4)^(2-)+2H^(+)rarrCr_(2)O_(7)^(2-)+H_(2)O`