Question -
Answer -
(i) Transitionmetals and many of their compounds show paramagnetic
behaviour.
(ii) Theenthalpies of atomisation of the transition metals are high.
(iii) Thetransition metals generally form coloured compounds.
(iv) Transitionmetals and their many compounds act as good catalyst.
Answer
(i) Transitionmetals show paramagnetic behaviour. Paramagnetism arises due to the presence ofunpaired electrons with each electron having a magnetic moment associated withits spin angular momentum and orbital angular momentum. However, in the firsttransition series, the orbital angular momentum is quenched. Therefore, theresulting paramagnetism is only because of the unpaired electron.
(ii) Transitionelements have high effective nuclear charge and a large number of valenceelectrons. Therefore, they form very strong metallic bonds. As a result, theenthalpy of atomization of transition metals is high.
(iii) Mostof the complexes of transition metals are coloured. This is because of theabsorption of radiation from visible light region to promote an electron fromone of the d−orbitals to another. In the presence of ligands,the d-orbitals split up into two sets of orbitals having differentenergies. Therefore, the transition of electrons can take place from one settoanother. The energy required for these transitions is quite small and fallsin the visible region of radiation. The ions of transition metals absorb theradiation of a particular wavelength and the rest is reflected, impartingcolour to the solution.
(iv) Thecatalytic activity of the transition elements can be explained by two basicfacts.
(a) Owingto their ability to show variable oxidation states and form complexes,transition metals form unstable intermediate compounds. Thus, they provide anew path with lower activation energy, Ea, for thereaction.
(b) Transitionmetals also provide a suitable surface for the reactions to occur.