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प्रश्न
Account for the following :
Zr and Hf have almost similar atomic radii.
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उत्तर
Due to lanthanide contraction, Zr and Hf have almost similar atomic radii. It can be explained on the basis of shielding effect. The electrons present in inner shells, shield the outer electrons from nuclear charge, making them experience a low effective nuclear charge. The shielding effect exerted by the electrons decreases in the order s > p > d > f. The f subshell poorly shields the outer electrons from nuclear attraction, which results in more attractive pull of nucleus on outer electron. In case of post lanthanide elements like Hf, 4f subshell is filled and it is not very effective at shielding the outer shell electrons. Therefore, Zr and Hf have almost similar atomic radii.
संबंधित प्रश्न
What are lanthanoids?
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.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.
Explain effects 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)
Although +3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?
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.
Name an important alloy which contains some of the lanthanoid metals. Mention its uses.
