Question

Give reasons for the following:
(i) Transition elements and their compounds act as catalysts.
(ii) $E^0$ value for $\left(M{n}^{2+}|Mn\right)$ is negative whereas for $\left(C{u}^{2+}|Cu\right)$ is positive.
(iii) Actinoids show irregularities in their electronic configuration.

Answer 1

(i) Transition metals and their compounds function as catalysts because of their ability to exhibit variable oxidation states and also their tendency to adsorb other substances on to their surface and activate them in the process.
(ii) E° value for $\left(M{n}^{2+}|Mn\right)$ is negative whereas for $\left(C{u}^{2+}|Cu\right)$ is positive as the hydration enthalpy of $C{u}^{2+}$ ion is not sufficient to compensate the sum of sublimation as well as first and second ionisation enthalpy of copper.
(iii) The irregularities in the electronic configurations of the actinoids are related to the stabilities of the $f^0,f^{7}and{f}^{14}$ occupancies of the $5f$ orbitals.