The d- and f-Block Elements — Chemistry STD 12 Science — Question

There are the following differences in the properties of first transition series elements and heavy transition elements : 
(i) Elements of the first transition series generally show +2 and +3 oxidation states, whereas in heavier transition elements, higher oxidation states are more stable.
(ii) The elements of the first transition series do not have metal-metal (M-M) bond which is generally found in heavy transition elements. For this reason, the melting points of heavy transition elements are higher than the melting points of the elements of the first transition series.
(iii) Elements of the first transition series do not form complexes with high coordination numbers, like 7 to 8, whereas heavy transition elements also form complexes with coordination numbers 7 or 8.
(iv) Nature of the ligand in the elements of the first transition series, on the basis of strength, low spin complexes and high spin complexes are formed, whereas heavy transition elements always form low spin complexes.