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प्रश्न
What is Lanthanoid contraction?
What do you understand by lanthanoid contraction?
What is lanthanoid contraction? Explain.
What is meant by Lanthanide contraction?
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उत्तर १
The lanthanide series of elements is defined as a gradual reduction in atom size, known as lanthanoid contraction. This reduction occurs due to insufficient shielding of additional electrons in the 4f subshell by filled 5s and 5p orbitals. As a result, the effective nuclear charge increases, resulting in smaller atomic sizes.
उत्तर २
- The size of the atoms and ions has been found to routinely decrease as one moves from cerium to lutetium. In the case of tripositive ions, this size reduction is more consistent.
- The nuclear charge rises with atomic number when one transitions from Ce to Lu, and the inner 4f-orbital gains the differentiating electron.
- The shielding of one 4f-electron by another from growing nuclear charge is imperfect due to the irregular geometries of 4f-orbitals.
- As a result, each 4f-electron experiences an increasing effective nuclear charge as the atomic number rises. As each electron in the 4f-subshell is added, the size is somewhat decreased.
- As a result, the size steadily contracts as the effective nuclear charge steadily rises with each additional electron in the 4f-subshell.
- Lanthanoid contraction refers to the cumulative effect of successive contractions on all lanthanoids.
- The total contraction in atomic radius in going from Ce to Lu is about 15 pm.
- Atomic radii show a tendency to decrease in size; however, the pattern is irregular.
Notes
Students can refer to the provided solutions based on their preferred marks.
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संबंधित प्रश्न
Define lanthanoid contraction.
What are chemical twins? Write ‘two’ examples.
What are lanthanoids?
What are the different oxidation states exhibited by the 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 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 different oxidation states of iron
Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?
Explain effects of lanthanoid contraction.
What are the consequences of lanthanoid contraction?
Account for the following:
Zn, Cd and Hg are soft metals.
Explain the cause of Lanthanoids 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
Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
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 |
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 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.
Which of the following pairs has the same ionic size?
Write any two consequences of Lanthanoid Contraction.
The lathanide ion that would show colour is ______.
Which one of the lanthanoids given below is the most stable in divalent form?
Mischmetal is an alloy consisting mainly of ______.
Write a note on lanthanoids.
Why is Mn2+ ion more stable than Fe2+ ion?
(Atomic numbers of Mn = 25 and Fe = 26)
Trivalent Lanthanoid ions such as La3+ (Z = 57) and Lu3+ (Z = 71) do not show any colour in their solution. Give a reason.
Name an important alloy which contains some of the lanthanoid metals.
Mention uses of alloys.
