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प्रश्न
What are chemical twins? Write ‘two’ examples.
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उत्तर
Chemical twins are those in which the properties of some elements are same. Atomic size of Zr and Hf , Nb and Ta are similar. This is due to Lanthanide contraction.
Example - Zr and Hf ; Nb and Ta
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संबंधित प्रश्न
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.
Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.
Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?
What is lanthanoid contraction? Write the.............
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
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 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:
Trends in the stability of oxo salts of lanthanoids from \[\ce{La}\] to \[\ce{Lu}\].
On the basis of Lanthanoid contraction, explain the following:
Radii of 4d and 5d block elements.
How would you account for the following:
There is a greater range of oxidation states among the actinoids than among the lanthanides.
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 ______.
Cerium (Z = S8) is an important member of lanthanoids. Which of the following statements about cerium is incorrect?
State a reason for the following:
La(OH)3 is more basic than Lu(OH)3.
Assertion: There is a continuous increase in size among Lanthanoids with an increase in atomic number.
Reason: Lanthanoids do not show Lanthanoid contraction.
Name an important alloy which contains some of the lanthanoid metals.
Name an important alloy which contains some of the lanthanoid metals. Mention its uses.
