Explain the following observations:
(i) In general the atomic radii of transition elements decrease with atomic number in a given series.
(ii) The for copper is positive (+0.34V). Copper is the only metal in the first series of transition elements showing this type of behaviour.
(iii) The E 0 value of Mn3 +/Mn2 + couple is much more positive than Cr3+/Cr2+ or Fe3+/Fe2+ couple.
i) The atomic radii decreases with the increase in atomic number as we move across the transition series. This is due to the poor shielding of d orbitals, which are unable to counter balance the effect of increasing nuclear charge.
ii) Copper is the only metal having positive electrode potential.
The reason for this is sum of enthalpies of sublimation and ionisation is not balanced by hydration enthalpy.
That is copper has low hydration enthalpy. This does not compensate the enthalpy of I and II ionisation energy of copper and sublimation energy.
iii) Mn2+ having d5 configuration is more stable as compare to Cr2+ having d4 configuration and Fe2+ having d6 configuration.
ii) Copper is the only metal having positive electrode potential.
The reason for this is sum of enthalpies of sublimation and ionisation is not balanced by hydration enthalpy.
That is copper has low hydration enthalpy. This does not compensate the enthalpy of I and II ionisation energy of copper and sublimation energy.
iii) Mn2+ having d5 configuration is more stable as compare to Cr2+ having d4 configuration and Fe2+ having d6 configuration.