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Question
Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.
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Solution 1
The lanthanides that exhibit +2 and +4 states are shown in the given table. The atomic numbers of the elements are given in parentheses.
| +2 | +4 |
| Nd (60) | Ce (58) |
| Sm (62) | Pr (59) |
| Eu (63) | Nd (60) |
| Tm (69) | Tb (65) |
| Yb (70) | Dy (66) |
After forming Ce4+, Ce attains a stable electronic configuration of [Xe].
After forming Tb4+, Tb attains a stable electronic configuration of [Xe] 4f7.
After forming Eu2+, Eu attains a stable electronic configuration of [Xe] 4f7.
After forming Yb2+, Yb attains a stable electronic configuration of [Xe] 4f14.
Solution 2
All lanthanoids show the Ln3+ oxidation state. But some of them also show +2 and +4 states in solution and solid forms, such as Ce4+, Eu2+, Yb2+, Tb4+, etc. The changing oxidation state correlates with electronic configuration owing to the enhanced stability of half-filled, fully filled, or vacant orbitals. e.g., Ce4+ has 4f0, Eu2+ has 4f7, Tb4+ has 4f7, and Yb2+ has 4f14 configuration.
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| Column I | Column II | |
| (i) | Oxidation state of Mn in MnO2 is | (a) + 2 |
| (ii) | Most stable oxidation state of Mn is | (b) + 3 |
| (iii) | Most stable oxidation state of | (c) + 4 |
| Mn in oxides is | (d) + 5 | |
| (iv) | Characteristic oxidation state of lanthanoids is | (e) + 7 |
Match the property given in Column I with the element given in Column II.
| Column I (Property) | Column II (Element) | |
| (i) | Lanthanoid which shows +4 oxidation state |
(a) Pm |
| (ii) | Lanthanoid which can show +2 oxidation state |
(b) Ce |
| (iii) | Radioactive lanthanoid | (c) Lu |
| (iv) | Lanthanoid which has 4f7 electronic configuration in +3 oxidation state |
(d) Eu |
| (v) | Lanthanoid which has 4f14 electronic configuration in +3 oxidation state |
(e) Gd |
| (f) Dy |
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On the basis of Lanthanoid contraction, explain the following:
Trends in acidic character of lanthanoid oxides.
Write any two consequences of Lanthanoid Contraction.
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La(OH)3 is more basic than Lu(OH)3.
Assertion: There is a continuous increase in size among Lanthanoids with an increase in atomic number.
Reason: Lanthanoids do not show Lanthanoid contraction.
The pair of lanthanoid ions which are diamagnetic is:
