(i) The transition metals generally form coloured compounds.
(ii) Transition metals and their many compounds act as good catalyst.

(i) Most of the complexes of transition metals are coloured as on the absorption of radiation from visible spectrum excites an electron to jump from one of the d−orbitals to another. In the presence of ligands, the d-orbitals split up into two sets of orbitals having different energies (as per crystal field theory). The energy required for these transitions is quite small and falls in the visible region of radiation. The ions of transition metals absorb the radiation of only a particular wavelength and the remaining is reflected back which imparts colour to the solution.

(ii) The catalytic activity of the transition elements can be explained by two basic facts.

(a) Transition metals provide a suitable surface (large surface area) for the reactions to occur.

(b) Owing to their ability to show variable oxidation states and formation of complexes, transition metals form unstable intermediate compounds. Thus, they provide a new path with lower activation energy, Ea, for the reaction.