(a) What is Lanthanoid contration ? What are its important effects ? (b) Account for the following : (i) `Zn^(2+)` salts are white while `Ni^(2+)` salts are coloured.
(ii) Ionisation enthalpies of 5d series elements are higher than the corresponding 3d series elements

First IE of 5d seties element are higher than those of 3d and 4d series elements. This is due to:

How will you account for the following : (i) All scandium salt are white. (ii) The first ionisation enthalpy of the 5d transition elements are higher than those of 3d and 4d transition elements in respective group.

Assing the reason for the following : (i) Transition metals generally form coloured compounds. (ii) Manganese exhibits highest oxidation state of +7 among the 3d series of transition elements.

(a) Why are Zn^(2+) salts white while Cu^(2+) salts are blue ? (b) What is meant by 'disproportionation' ? Write the disproportionation reaction of Cu^+ in aqueous solution.

How do you prepare : (i) k_(2)MnO_(4) from MnO_(2) ? (ii) Na_(2)Cr_(2)O_(7) from NaCrO_(4) ? (b) Account for the following : (i) Mn^(2+) is more stable then Fe^(2+) towards oxidation to + 3 state. (ii) The enthelpy of atomization is lowest for Zn in 3d series of the transition elements. (iii) Actinoid elements show wide range of oxidation states.