Lanthanide Contraction
Lanthanide contraction results in:
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Lanthanide contraction is responsible for:
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About This Question
- Subject
- chemistry
- Chapter
- d- and f-block elements
- Topic
- lanthanide contraction
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Decreasing basicity of hydroxides across lanthanide series
- Definition: As atomic number increases in the Lanthanide series (Ce to Lu), the atomic and ionic radii gradually decrease. This is the Lanthanide Contraction.
- Screening Effect: It happens because 4f electrons have poor shielding ability, allowing the nucleus to pull the outer electrons closer as nuclear charge increases.
- Consequence on Basicity: According to Fajan's rules, a smaller cation (Lu3+) has higher polarizing power than a larger cation (Ce3+).
- Covalent Nature: Therefore, the M2˘013OH bond becomes more covalent as we move from Ce to Lu.
- Result: The ability to release OH− ions decreases, meaning basicity decreases across the series (Ce(OH)3 is most basic, Lu(OH)3 is least basic).
This medium difficulty chemistry question is from the chapter d- and f-block elements, covering the topic of lanthanide contraction. It appeared in the 2025 exam.
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