Q. 324.4( 5 Votes )
Name the members of the lanthanide series which exhibit +4 oxidation states and those which exhibit +2 oxidation state. Try to correlate this type of behaviour with the electronic configuration of these elements.
The members of lanthanide series along with their electronic configuration are given in the below table:
The typical oxidation state of the lanthanides is +3. The oxidation state of +2 and +4 are exhibited by some of the elements. These are shown by those elements which by losing 2 or 4 elements acquire a stable configuration.
+2 oxidation state is exhibited when the lanthanide has the configuration 5d06s2 so that 2 electrons are lost easily. Hence the members which will show +2 oxidation state are:
+2 = 60Nd, 62Sm, 63Eu, 69Tm, 70Yb
+4 oxidation state is exhibited when the configuration left (by losing 2 electrons) is close to 4f0 (example 4f0 , 4f1, 4f2, 4f3) or close to 4f7 (example 4f7or 4f8) or close to 4f14 ( 4f13 or 4f14)
Hence, the members which will show +4 oxidation state are:
+4 = 58Ce, 59Pr, 60Nd, 65Tb, 66Dy
Note: Each case tends to revert to the more stable oxidation state of +3 by loss or gain of an electron. That is why Sm2+, Eu2+ and Yb2+ ions in solutions are good reducing agents and aqueous solution of Ce4+ and Tb4+ are good oxidizing agents.
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On the basis of Lanthanoid contraction, explain the following :
(i) Nature of bonding in La2O3 and Lu2O3.
(ii) Trends in the stability of oxo salts of lanthanoids from La to Lu.
(iii) Stability of the complexes of lanthanoids.
(iv) Radii of 4d and 5d block elements.
(v) Trends in acidic character of lanthanoid oxides.
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