Question

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

• A. $Yb^{3+} < Pm^{3+} < Ce^{3+} < La^{3+}$
• B. $Ce^{3+} < Yb^{3+} < Pm^{3+} < La^{3+}$
• C. $Yb^{3+} < Pm^{3+} < La^{3+} < Ce^{3+}$
• D. $Pm^{3+} < La^{3+} < Ce^{3+} < Yb^{3+}$

Answer 1

Answer: (A)

Ionic radii decrease as we move across lanthanide series due to lanthanide contraction. As all ion are in 3 + oxidation state, ionic radii will follow the trend of atomic radii
$La^{3+}> Ce^{3+} >Pm^{3+} > Yb^{3+} $
$Yb^{3+} < Pm^{3+} < Ce^{3+} < La^{3+}$
[At. No. La = 57, Ce = 58, Pm = 61, Yb = 70]