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]

Answer 1

$\begin{array}{cccc}& +2& +3& +4\\ \text{Eu}& 4f^7& 4f^6& \\ \text{Tm}& 4f^{13}& 4f^{12}& \\ \text{Sm}& 4f^6& 4f^5& \\ \text{Tb}& 4f^9& 4f^8& 4f^7\\ \text{Yb}& 4f^{14}& 4f^{13}& \\ \text{Dy}& 4f^{10}& 4f^9& \end{array}$
Hence, the pair $T{b}^{+4}Y{b}^{+2}$ have half filled and completely filled f subshells respectively.