(a) What is meant by the term lanthanoid contraction ? What is it due to and what consequences does it have on the chemistry of elements following lanthanoids in the periodic table ?
(b) Explain the following observations :
(i) `Cu^(+)` ion is unstable in aqueous solutions .
(ii) Although `Co^(2+)` ion appears to be stable , it is easily oxidised to `Co^(3+)` ion in the presence of a strong ligand.
(iii) The `E_(Mn^(2+)//Mn)^(@)` value for manganese is much more than expected from the trend for other elements in the series.