Account for the following:

(i) Transition metals form coloured compounds.

(ii) Actinoids show wide range of oxidation states.

(iii) Zinc has lowest enthalpy of atomization in 3d series.

OR

What must be the stable oxidation states of the transition elements with the following configuration in the ground state of their atoms: 3d³, 3d⁵, 3d⁸, 3d⁴

(i) Transition metals form colored compounds because they have unpaired electrons in the (n-1) d orbital which show d-d transition and thus exhibit different colors.

(ii) Actinoids show wide range of oxidation states due to comparable energies of 5f, 6d and 7s orbitals. Moreover, 5f orbitals are not as buried as 4f and hence 5f electrons can participate in bonding.

(iii) Zinc has lowest enthalpy of atomization in 3d series because zinc has completely filled d orbitals (3d¹⁰4s²) due to which it cannot take part in bond formation as it does not have any unpaired electron. Thus, it has lowest enthalpy of atomization,

OR

The stable oxidation states of the transition elements with the following configuration in the ground state of their atoms are