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Karnataka Board PUCPUC Science 2nd PUC Class 12

Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes.

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Question

Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes.

Long Answer
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Solution

Both lanthanoids and actinoids show a progressive decrease in the size of their atoms and ions (M3+) across the series. In lanthanoids, this decrease is called lanthanoid contraction, while in actinoids, it is called actinoid contraction.
However, the decrease in size between two successive elements is higher in actinoids than in lanthanoids (i.e., actinoid contraction is more pronounced than lanthanoid contraction). This is because 5f electrons provide a poorer screening/shielding effect than 4f electrons, causing the outer electrons in actinoids to experience a stronger effective nuclear charge.
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Chapter 4: d-and ƒ-Block Elements - REVIEW EXERCISES [Page 492]

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Nootan Chemistry [English] Class 12 ISC
Chapter 4 d-and ƒ-Block Elements
REVIEW EXERCISES | Q 8.58 (i) | Page 492
Nootan Chemistry [English] Class 12 ISC
Chapter 4 d-and ƒ-Block Elements
'NCERT TEXT-BOOK, Exercises | Q 8.20 (ii) | Page 507
NCERT Chemistry Part 1 and 2 [English] Class 12
Chapter 4 The d-block and f-block Elements
Exercises | Q 4.20 (ii) | Page 116

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