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  4. Assertion: La(OH)3 is more basic than Lu(OH)3. Reason: Size of Lu3+ increases and shows more covalent character.

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Q. Assertion : $La(OH)_3$ is more basic than $Lu(OH)_3$.
Reason : Size of $Lu^{3+}$ increases and shows more covalent character.

AIIMSAIIMS 2012The d-and f-Block Elements

Solution:

Due to lanthanide contraction, the size of Lu3+ is decreased and therefore Lu(OH)3 shows more covalent character (Small cation, more is covalent character - Fajan’s rule). Thus La(OH)3 is more ionic and thus more basic.