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प्रश्न
Define lanthanoid contraction.
What is lanthanoid contraction?
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उत्तर
In the lanthanoids, the electrons are filling the 4f-subshell. On moving from left to right, the nuclear charge increases, and this increase is expected to be compensated by the increase in the magnitude of the shielding effect by the 4f-electrons. However, the f-electrons have very poor shielding effects. With an increasing atomic number in the lanthanoid series, there is a progressive decrease in the atomic as well as ionic radii of trivalent ions from La3+ to Lu3+, and this is known as lanthanoid contraction.
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?
Account for the following :
Zr and Hf have almost similar atomic radii.
What are the different oxidation states exhibited by the lanthanoids?
Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes.
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?
What are the consequences of lanthanoid contraction?
Which trivalent ion has the maximum size in the Lanthanoid series, i.e., Lanthanum ion (La3+) to Luteium ion (Lu3+)?
(at. no. of Lanthanum = 57 and Lutetium = 71)
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 the action of the following on lanthanoids?
a. water
b. Sulphur, heat
c. nitrogen, heat
What is lanthanoid contraction?
The f-block elements are known as ____________.
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)
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 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 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:
Stability of the complexes of lanthanoids.
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:-
Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of ______.
The lathanide ion that would show colour is ______.
Mischmetal is an alloy consisting mainly of ______.
Write a note on lanthanoids.
State a reason for the following:
La(OH)3 is more basic than Lu(OH)3.
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.
Assertion: There is a continuous increase in size among Lanthanoids with an increase in atomic number.
Reason: Lanthanoids do not show Lanthanoid contraction.
The pair of lanthanoid ions which are diamagnetic is:
