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प्रश्न
Which among the following pairs of elements is 'not' an example of chemical twins?
पर्याय
Zr and Hf
Nb and Ta
Mo and W
Ta and Re
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उत्तर
Ta and Re
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संबंधित प्रश्न
Define lanthanoid contraction.
What are chemical twins? Write ‘two’ examples.
What are lanthanoids?
Account for the following :
Zr and Hf have almost similar atomic radii.
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.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.
Explain effects 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 lanthanoid contraction? Write the.............
What is Lanthanoid contraction?
The f-block elements are known as ____________.
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 |
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:
Nature of bonding in \[\ce{La2O3}\] and \[\ce{Lu2O3}\] .
Which of the following pairs has the same ionic size?
In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.
Which one of the lanthanoids given below is the most stable in divalent form?
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.
