Question

(a) Account for the following:
(i) Transition metals show variable oxidation states.
(ii) Zn, Cd and Hg are soft metals.
(iii) $E^o$ value for the $M{n}^{3+}/M{n}^{2+}$ couple is highly positive (+ 1.57 V) as compared to $C{r}^{3+}/C{r}^{2+}$.
(b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Answer 1

(a)(i) Transition metals exhibit variable oxidation states due to different energy requirements.
(ii) Because they do not exhibit covalency as their (n-1)d orbital is fully filled, So they are soft.
(iii) Because Mn is more reactive than Cr.
(b) Difference:
$$\begin{array}{cc}\text{Lanthanoid}& \text{Actinoid}\\ \text{- Less tendency of complex formation.}& \text{- High tendency of complex formation.}\\ \text{- do not form oxo cations.}& \text{-Form oxo cation.}\end{array}$$

Similarity : In both cases f- orbitals are progressively filled.