Pair of ions which are having only one unpair electron

1.	Pair of ions which are having only one unpair electron
Answer» `CE^(3+), Yb^(3+)` `EU^(3+), Tb^(3+)` `Pm^(3+), Sm^(3+)` `DY^(3+), Tb^(3+)` Answer :A

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