Explain the following trends in the properties of the members of the F

1.	Explain the following trends in the properties of the members of the First series of transition elements:(i) (M2+/M) value for copper is positive(+0.34 V) in contrast to the other members of the series.(ii) Cr2+ is reducing while Mn3+ is oxidising, though both have d4 configuration.(iii) The oxidising power in the series increases in the order VO+2 < Cr2O2-7 < MnO4-.
Answer» (i) Copper has high enthalpy of atomisation and low enthalpy of hydration. Since the high energy to transform Cu(s) to Cu²⁺(aq) is not balanced by hydration enthalpy, therefore E°(M²⁺/M)value for copper is positive(+0.34 V). (ii) Cr²⁺ is reducing as its configuration changes from d⁴ to d³ , the latter having more stable half filled t_2g level. On the other hand, the change from Mn³⁺ to Mn²⁺ results in extra stable d⁵ configuration. (iii) This is due to the increasing stability of the species of lower oxidation state to which they are reduced.

Explain the following trends in the properties of the members of the First series of transition elements:(i) (M2+/M) value for copper is positive(+0.34 V) in contrast to the other members of the series.(ii) Cr2+ is reducing while Mn3+ is oxidising, though both have d4 configuration.(iii) The oxidising power in the series increases in the order VO+2 < Cr2O2-7 < MnO4-.

Answer»

(i) Copper has high enthalpy of atomisation and low enthalpy of hydration. Since the high energy to transform Cu(s) to Cu²⁺(aq) is not balanced by hydration enthalpy, therefore E°(M²⁺/M)value for copper is positive(+0.34 V).

(ii) Cr²⁺ is reducing as its configuration changes from d⁴ to d³ , the latter having more stable half filled t_2g level. On the other hand, the change from Mn³⁺ to Mn²⁺ results in extra stable d⁵ configuration.

(iii) This is due to the increasing stability of the species of lower oxidation state to which they are reduced.

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