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JEE Main levelSingle correct optionDifficulty 2 of 3df190

Among the following actinoids, the one whose most stable oxidation state is $+ 4$ rather than $+ 3$ is

A $Am$
B $Th$
C $Lr$
D $Cm$

Answer: B

Th (

6 d^{2} 7 s^{2}

) loses all four valence electrons to give the radon-core

Th X^{4 +}

. Am, Cm and Lr are most stable as

M X^{3 +}

.

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