Statement (I) Co^{2+} has a higher magnetic m | vedclass

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(D) For Statement $(I)$:The electronic configuration of $Co^{2+}$ is $[Ar] 3d^7$. It has $n = 3$ unpaired electrons.The magnetic moment $\mu = \sqrt{n

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$(I)$ is not correct but $(II)$ is correct

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(D) For Statement $(I)$:The electronic configuration of $Co^{2+}$ is $[Ar] 3d^7$. It has $n = 3$ unpaired electrons.The magnetic moment $\mu = \sqrt{n(n+2)} = \sqrt{3(3+2)} = \sqrt{15} \approx 3.87 \ B.M$.The electronic configuration of $Cr^{3+}$ is $[Ar] 3d^3$. It has $n = 3$ unpaired electrons.Wait,$Cr^{3+}$ is $3d^3$ $(n=3)$,so $\mu = \sqrt{3(5)} = 3.87 \ B.M$. Actually,$Cr^{3+}$ has $3$ unpaired electrons and $Co^{2+}$ has $3$ unpaired electrons. Thus,their magnetic moments are similar. The statement claiming $Co^{2+}$ has a higher magnetic moment is incorrect.For Statement $(II)$:The ionisation enthalpies of lanthanoids $(Ce, Pr, Nd)$ are generally higher than those of actinoids $(Th, Pa, U)$ because $4f$ electrons are more effectively shielded than $5f$ electrons,making the valence electrons in actinoids more loosely held.Therefore,Statement $(I)$ is incorrect and Statement $(II)$ is correct. The correct option is $(D)$.

Statement $(I)$ $Co^{2+}$ has a higher magnetic moment than $Cr^{3+}$.
Statement $(II)$ Ionisation enthalpies of $Ce$,$Pr$ and $Nd$ are higher than $Th$,$Pa$ and $U$.
Which of the following is correct?

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Statement $(I)$ $Co^{2+}$ has a higher magnetic moment than $Cr^{3+}$.Statement $(II)$ Ionisation enthalpies of $Ce$,$Pr$ and $Nd$ are higher than $Th$,$Pa$ and $U$.Which of the following is correct?