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प्रश्न
Explain the cause of Lanthanoids contraction.
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उत्तर
- In the Lanthanoid series with increasing atomic number, the atomic and ionic radii decrease from one element to another but a decrease is very small.
- An increase in nuclear charge in a period increases the force of attraction towards the outer electrons. Hence
atomic size or radius decreases. - Filling of the electrons in the inner shells increases the atomic size as inner electrons repel outer electrons. The shielding effect of electrons decreases in the order s > p > d > f
- The new electrons are added to the same inner 4f orbital. Hence, Lanthanoid contraction is due to
- Poor shielding effect of the 4f electrons
- Increase in nuclear charge.
- Non-introduction of new outer shells.
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संबंधित प्रश्न
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.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.
The chemistry of the actinoid elements is not so smooth as that of the Lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.
Write the electronic configurations of the element with the atomic number 61.
Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?
What are the consequences of lanthanoid contraction?
Name an element of lanthanoid series which is well knwon to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent?
What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements.
What is the action of the following on lanthanoids?
a. water
b. Sulphur, heat
c. nitrogen, heat
What is Lanthanoid contraction?
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) \[\ce{Ho}\]
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 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 |
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:
Radii of 4d and 5d block elements.
On the basis of Lanthanoid contraction, explain the following:
Trends in acidic character of lanthanoid oxides.
In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.
The lathanide ion that would show colour is ______.
Mischmetal is an alloy consisting mainly of ______.
Why is Mn2+ ion more stable than Fe2+ ion?
(Atomic numbers of Mn = 25 and Fe = 26)
Name an important alloy which contains some of the lanthanoid metals.
