NCERT Class XII Chemistry
Chapter - The d- and f-Block Elements
Questions with Solutions
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Question : 35
Total: 49
Compare the general characteristics of the first series of transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points
(i) electronic configurations
(ii) oxidation states
(iii) ionisation enthalpies and
(iv) atomic sizes.
(i) electronic configurations
(ii) oxidation states
(iii) ionisation enthalpies and
(iv) atomic sizes.
Solution:
(i) Electronic configurations : In ls t n d r d
(ii) Oxidations states : Elements show variable oxidation states in boththe series. The highest oxidation state is equal to total number of electronsin ‘s’ as well as ‘d’ orbitals. The number of oxidation states shown are lessin 5d transition series than 4d series. In 3d series +2 and +3 oxidation statesare common and they form stable complexes in these oxidation states. Inother seriesO s O 4 P t F 6
(iii)Ionisation enthalpies : The ionisation enthalpies in each seriesgenerally increases gradually from left to right. The ionisation enthalpyof 5d series do not differ appreciably due to lanthanoid contraction.
(iv) Atomic sizes : The atomic sizes of 4d and 5d-series do not differappreciably due to lanthanoid contraction. The atomic radii of secondand third series are larger than 3d series.
(ii) Oxidations states : Elements show variable oxidation states in boththe series. The highest oxidation state is equal to total number of electronsin ‘s’ as well as ‘d’ orbitals. The number of oxidation states shown are lessin 5d transition series than 4d series. In 3d series +2 and +3 oxidation statesare common and they form stable complexes in these oxidation states. Inother series
(iii)Ionisation enthalpies : The ionisation enthalpies in each seriesgenerally increases gradually from left to right. The ionisation enthalpyof 5d series do not differ appreciably due to lanthanoid contraction.
(iv) Atomic sizes : The atomic sizes of 4d and 5d-series do not differappreciably due to lanthanoid contraction. The atomic radii of secondand third series are larger than 3d series.
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