Chapter 8 The d and f Block Elements Solutions
Question - 41 : - Which is the last element in the series of the actinoids? Write theelectronic configuration of this element. Comment on the possible oxidationstate of this element.
Answer - 41 : -
Lawrencium (Lr) is the last element ofactinoids. Its outer electronic configuration is 5f14 6d1 7s2 andits possible oxidation state is +3.
Question - 42 : - Use Hund’s rule to derive the electronic configuration of Ce3+ ion,and calculate its magnetic moment on the basis of ‘spin-only’ formula.
Answer - 42 : - The electronic configuration of Ce3+ is 4f1
Question - 43 : - Name the members of the lanthanoid series which exhibit +4 oxidationstate and those which exhibit +2 oxidation state. Try to correlate this type ofbehaviour with the electronic configurations of these elements.
Answer - 43 : -
All lanthanoids show Ln3+ oxidationstate. But some of them show +2 and +4 states also in solution and solid formlike Ce4+, Eu2+, Yb2+, Tb4+, etc.The variable oxidation state is related to electronic configuration due toextra stability of half filled, fully filled or empty orbitals, e.g., Ce4+ has4f0, Eu2+ has 4f7 Tb4+ has4f7 and Yb2+ has 4f14 configuration.
Question - 44 : - Write the electronic configurations of the elements with the atomicnumbers 61,91,101, and 109.
Answer - 44 : - 
Question - 45 : - 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.
Answer - 45 : - Give special emphasis on the following points
(i) electronicconfigurations
(ii) oxidation states
(iii) ionisation enthalpiesand
(iv) atomic sizes.
Answer
(i) Electronicconfigurations : In 1st transitionseries, 3d-orbitals are progressively filled whereas in 2nd transitionseries, 4d-orbitals are progressively filled and in 3rd transitionseries, 5d-orbitals are progressively filled.
(ii) Oxidationsstates : Elements show variable oxidation statesin both the series. The highest oxidation state is equal to total number ofelectrons in ‘s’ as well as ‘d’ orbitals. The number of oxidation states shownare less in 5d transition series than 4d series. In 3d series +2 and +3oxidation states are common and they form stable complexes in these oxidationstates. In other series OsO4 and PtF6 areformed which are quite stable in higher oxidation state.
(iii) Ionisationenthalpies : The ionisation enthalpies in each seriesgenerally increases gradually from left to right. The ionisation enthalpy of 5dseries 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 second and thirdseries are larger than 3d series.
Answer - 46 : - Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).
Answer
Question - 47 : - Comment on the statement that elements of the first transition series possessmany properties different from those of heavier transition elements.
Answer - 47 : -
1. In first transitionseries lower oxidation state is more stable whereas in heavier transitionelements higher oxidation states are more stable.
2. The ionisationenthalpy of 5d transition series is higher than 3d and 4d transition series.
3. M-M bonding is most commonin heavier transition metals but less in first series.
4. The elements of firsttransition series do not form complexes with higher coordination number of 7and 8.
5. The elements of firstseries can form high spin or low spin complexes depending upon strength ofligands but elements of other series form low spin complexes irrespective ofstrength of ligands.
Question - 48 : - What can be inferred from the magnetic moment values of the followingcomplex species?
Answer - 48 : - 
Answer