Question

Explain given reasons:

(i) Transition metals and many of their compounds show paramagnetic behaviour.
(ii) The enthalpies of atomisation of the transition metals are high.

(iii) The transition metals generally form coloured compounds.

(iv) Transition metals and their many compounds act as good catalyst.

Answer 1

(i) Transition metals and many of their compounds show paramagnetic behaviour.
This is due to presence of one or more unpaired electrons in d subshell.
(ii) The enthalpies of atomisation of the transition metals are high.
This is due to high effective nuclear charge and large number of valence electrons. This results in formation of strong metallic bonds.
(iii) The transition metals generally form coloured compounds.
This is due to d-d transition of unpaired electrons. In presence of ligands, the d orbitals split into two sets. Transition metal ions absorb radiation of a particular wavelength and reflect the remaining. This imparts colour.
(iv) Transition metals and their many compounds act as good catalyst.
Transition metals show variable oxidation states and forms complexes. They form unstable intermediate compounds. They provide a new path with lower activation energy of reaction. They also provide a suitable surface for the reaction to occur.