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प्रश्न
Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?
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उत्तर
57La -Electronic configuration is [Xe]4f0 5d1 6s2
After losing 3 electrons La forms La3+ ion which is stable due to empty 4f-orbitals.
58Ce - Electronic configuration is [Xe]4f2 5d0 6s2
After losing 4 electrons Ce forms Ce4+ ion which is stable due to empty 4f-orbitals.
Thus, lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion.
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संबंधित प्रश्न
What are chemical twins? Write ‘two’ examples.
What are lanthanoids?
Which among the following pairs of elements is 'not' an example of chemical twins?
Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
What are the different oxidation states exhibited by the lanthanoids?
Compare the chemistry of actinoids with that of the lanthanoids with special reference to oxidation state.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.
Write the electronic configurations of the element with the atomic number 61.
Write the different oxidation states of iron
Account for the following:
Zn, Cd and Hg are soft metals.
What is Lanthanoid contraction?
General electronic configuration of actinoids is `(n-2)f^(1-14)(n - 1)d^(0-2)ns^2`.Which of the following actinoids have one electron in 6d orbital?
(i) U (Atomic no. 92)
(ii) Np (Atomic no.93)
(iii) Pu (Atomic no. 94)
(iv) Am (Atomic no. 95)
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+
Although +3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?
Match the compounds/elements given in Column I with uses given in Column II.
| Column I (Compound/element) | Column II (Use) | |
| (i) | Lanthanoid oxide | (a) Production of iron alloy |
| (ii) | Lanthanoid | (b) Television screen |
| (iii) | Misch metal | (c) Petroleum cracking |
| (iv) | Magnesium based alloy is constituent of | (d) Lanthanoid metal + iron |
| (v) | Mixed oxides of lanthanoids are employed | (e) Bullets |
| (f) In X-ray screen |
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 |
On the basis of Lanthanoid contraction, explain the following:
Trends in the stability of oxo salts of lanthanoids from \[\ce{La}\] to \[\ce{Lu}\].
On the basis of Lanthanoid contraction, explain the following:
Stability of the complexes of lanthanoids.
On the basis of Lanthanoid contraction, explain the following:
Trends in acidic character of lanthanoid oxides.
Which of the following pairs has the same ionic size?
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 ______.
The lathanide ion that would show colour is ______.
Which one of the lanthanoids given below is the most stable in divalent form?
State a reason for the following:
La(OH)3 is more basic than Lu(OH)3.
Name an important alloy which contains some of the lanthanoid metals.
