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JEE Main levelOne or more correct optionsDifficulty 2 of 3df198

Which of the following statements are correct?

ATh is most commonly encountered in the $+ 4$ state
BAll actinoids are radioactive
C $Lr X^{3 +}$ has the $5 f^{14}$ configuration
D $5 f$ electrons shield the nuclear charge better than $4 f$ electrons

Answer: A, B, C

Every actinoid is radioactive, Th commonly forms

Th X^{4 +}

, and removal of the three outer electrons of Lr leaves a filled

5 f^{14}

subshell. The

5 f

electrons shield worse than

4 f

, which is why the actinoid contraction is larger.

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