Complete the following chemical equations:



Or

State reasons for the following:

(i) Cu (I) ion is not stable in an aqueous solution.

(ii) Unlike Cr^3+, Mn^2+, Fe³⁺ and the subsequent other M²⁺ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species.

(i) In aqueous solution, Cu⁺ ion undergoes oxidation to Cu²⁺ ion. The relative stability of different oxidation states can be seen from their electrode potentials.

Cu⁺(aq) + e^- --> Cu(s) , E⁰_red = 0.52V

Cu²⁺(aq) + 2e­^- ---> Cu(s), E⁰_red = 0.34V

Thus overall reaction is :

2Cu⁺ (aq) ---> Cu²⁺ (aq) + Cu(s)

Due to more reduction electrode potential value of Cu⁺, it undergoes oxidation reaction quite feasibly. Hence, copper (I) ion is not stable in aqueous solution.

(ii) The valence shell electronic configurations of Cr^3+, Mn^2+, Fe³⁺ are d³, d⁵ and d³respectively. Owing to the symmetrical distribution of the d electrons, these ions can form stable cationic complexes. The atomic radii of the 4d and 5d transition elements are more than that of the 3d series elements. Hence, generally, they do not form stable cationic species.