, , and have ionic radii in the increasing order as

Question

, ,  and  have ionic radii in the increasing order as

Canvas Classes · Accepted Answer

🧠 Lanthanoid contraction: higher  within the  series means smaller ionic radius
Each additional  electron adds poor shielding, so effective nuclear charge rises and the ion shrinks. La () is the first, Ce () is next, Pm () is later, and Yb () is near the end.

🗺️ Apply the contraction
La (): earliest, largest.
Ce (): slightly smaller.
Pm (): even smaller.
Yb (): latest in the series, smallest.

Decreasing order: La  Ce  Pm  Yb.

The question asks for increasing order:

⚠️ Common mistake
Optio

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