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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3df205

Which of the following are consequences of lanthanoid contraction?

AThe basic strength of $Ln (OH) X_{3}$ decreases from La to Lu
BThe ionic radius of $Ln X^{3 +}$ increases from La to Lu
CZr and Hf are very difficult to separate chemically
DThe atomic radius of Ta is almost the same as that of Nb

Answer: A, C, D

Poor

4 f

shielding makes the sizes of Zr/Hf and Nb/Ta nearly identical, so their chemistry is alike and separation is hard. Smaller

Ln X^{3 +}

ions polarise the hydroxide more and reduce basicity. The ionic radius decreases (not increases) from La to Lu.

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