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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
What are lanthanoids?
Compare the chemistry of actinoids with that of lanthanoids with special reference to electronic configuration.
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 atomic and ionic sizes.
Write the electronic configuration of the element with the atomic number 61.
What are the consequences of lanthanoid contraction?
Account for the following:
Zn, Cd and Hg are soft metals.
What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements.
What is lanthanoid contraction?
Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
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 Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?
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 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:
Nature of bonding in \[\ce{La2O3}\] and \[\ce{Lu2O3}\] .
On the basis of Lanthanoid contraction, explain the following:
Trends in acidic character of lanthanoid oxides.
How would you account for the following:
There is a greater range of oxidation states among the actinoids than among the lanthanides.
Which of the following pairs has the same ionic size?
The titanium (Z = 22) compound that does not exist is:-
In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.
Mischmetal is an alloy consisting mainly of ______.
Cerium (Z = S8) is an important member of lanthanoids. Which of the following statements about cerium is incorrect?
Why is Mn2+ ion more stable than Fe2+ ion?
(Atomic numbers of Mn = 25 and Fe = 26)
The pair of lanthanoid ions which are diamagnetic is:
