Which property of transition metals enables them to behave as catalysts?
(a) Why is chemistry of actinoids complicated as compared to lanthanoids?
(b) Complete the following reaction and justify that it is a disproportionation reaction:
$$3 \mathrm{MnO}_4^{2-}+4 \mathrm{H}^{+} \rightarrow$$________ $$+$$ _________ $$+$$ $$\mathrm{H}_2 \mathrm{O}$$.
(c) The given graph shows the trends in melting points of transition metals:
Explain the reason why $$\mathrm{Cr}$$ has highest melting point and manganese $$(\mathrm{Mn})$$ a lower melting point.
