Question

The ′f′ orbitals are half and completely filled, respectively in lanthanide ions
[Given: Atomic no. Eu, 63; Sm, 62; Tm, 69; Tb, 65; Yb, 70; Dy, 66]

• A. $Eu^{2+}$ and $Tm^{2+}$
• B. $Sm^{2+}$ and $Tm^{3+}$
• C. $Tb^{4+}$ and $Yb^{2+}$
• D. $Dy^{3+}$ and $Yb^{3+}$

Answer 1

Answer: (C)

$Tb^{4+}$ and $Yb^{2+}$

Answer 2

| +2| +3| +4
---|---|---|---
Eu| $4f^7$| $4f^6$|
Tm| $4f^{13}$| $4f^{12}$|
Sm| $4f^6$| $4f^5$|
Tb| $4f^9$| $4f^8$| $4f^7$
Yb| $4f^{14}$| $4f^{13}$|
Dy| $4f^{10}$| $4f^9$|

Hence, the pair $Tb^{+4} Yb^{+2}$ have half filled and completely filled $f$ subshells respectively.