Lanthanoids
Lanthanoid contraction primarily occurs due to:
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About This Question
- Subject
- chemistry
- Chapter
- d- and f-block elements
- Topic
- lanthanoids
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Poor shielding by 4f electrons
Across the lanthanoid series, atomic number increases and nuclear charge rises steadily. However, 4f electrons shield very poorly, so effective nuclear charge felt by outer electrons increases significantly. This causes gradual decrease in ionic and atomic radii, known as lanthanoid contraction. The trend is not due to decreasing nuclear charge or full 5d filling.
This easy difficulty chemistry question is from the chapter d- and f-block elements, covering the topic of lanthanoids. It appeared in the 2025 exam.
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