Arrange Ce^{+3}, La^{+3}, Pm^{+3} and Yb^{+3} | vedclass

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(A) In the lanthanoid series,as the atomic number increases from $La$ $(Z=57)$ to $Lu$ $(Z=71)$,the ionic radii of the $M^{+3}$ ions decrease due to l

Vedclass · Accepted Answer

$Yb^{+3} < Pm^{+3} < Ce^{+3} < La^{+3}$

Vedclass · Answer

(A) In the lanthanoid series,as the atomic number increases from $La$ $(Z=57)$ to $Lu$ $(Z=71)$,the ionic radii of the $M^{+3}$ ions decrease due to lanthanoid contraction. This is because the $4f$ electrons provide poor shielding,causing the effective nuclear charge to increase,which pulls the electrons closer to the nucleus. The order of atomic numbers is $La$ $(57)$ Therefore,the order of ionic radii is $La^{+3} > Ce^{+3} > Pm^{+3} > Yb^{+3}$. In increasing order,this is $Yb^{+3} < Pm^{+3} < Ce^{+3} < La^{+3}$.

Arrange $Ce^{+3}, La^{+3}, Pm^{+3}$ and $Yb^{+3}$ in increasing order of their ionic radii.

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