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प्रश्न
Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?
(i) \[\ce{Ce}\]
(ii) \[\ce{Eu}\]
(iii) \[\ce{Yb}\]
(iv) \[\ce{Ho}\]
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उत्तर
(ii) \[\ce{Eu}\]
(iii) \[\ce{Yb}\]
Explanation:
\[\ce{Ce}\] (Z = 57) = [Xe] 4f5 5d0 6s2, O.S. = + 3, + 4
\[\ce{Eu}\] (Z = 63) = [Xe] 4f7 5d0 6s2, O.S. = + 2, + 3
\[\ce{Yb}\] (Z = 70) = [Xe] 4f14 5d0 6s2, O.S. = + 2, + 3
\[\ce{Ho}\] (Z = 67) = [Xe] 4f11 5d0 6s2, O.S. = + 3
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a. water
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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
(iv) it resembles Pb4+
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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Radii of 4d and 5d block elements.
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Trends in acidic character of lanthanoid oxides.
How would you account for the following:
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Mischmetal is an alloy consisting mainly of ______.
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Trivalent Lanthanoid ions such as La3+ (Z = 57) and Lu3+ (Z = 71) do not show any colour in their solution. Give a reason.
Assertion: There is a continuous increase in size among Lanthanoids with an increase in atomic number.
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