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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.
Solution
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.
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Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because:
(i) it has variable ionisation enthalpy
(ii) it has a tendency to attain noble gas configuration
(iii) it has a tendency to attain f 0 configuration
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Match the statements given in Column I with the oxidation states given in Column II.
| 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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Stability of the complexes of lanthanoids.
On the basis of Lanthanoid contraction, explain the following:
Radii of 4d and 5d block elements.
How would you account for the following:
There is a greater range of oxidation states among the actinoids than among the lanthanides.
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In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.
Zr(Z = 40) and Hf(Z = 72) have similar atomic and ionic radii because of ______
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Cerium (Z = S8) is an important member of lanthanoids. Which of the following statements about cerium is incorrect?
Write a note on lanthanoids.
Name an important alloy which contains some of the lanthanoid metals.
