Q13 of 30 Page 1

Assign reasons for the following:

(i) Copper (I) ion is not known in aqueous solution.


(ii) Actinoids exhibit greater range of oxidation states than lanthanoids.


(i) In aqueous solution Cu+ undergoes disproportionation to form a more stable Cu2+ ion.
2Cu2+ (aq) → Cu2+ (aq) + Cu(s)
The higher stability of Cu2+ ion is aqueous solution may be attributed to its greater negative ΔhydH than that of Cu+ ion. It compensates the second ionisation enthalpy of Cu involved in the formation of Cu2+ions.


(ii) Actinoids exhibit greater range of oxidation states than lanthanoids. This is because there is less energy difference between 5d and 6d orbitals belonging to actinoids than the energy difference between 4d and 5d orbitals in case of lanthanoids.


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