Question

The electronic configurations of bivalent europium and trivalent cerium are :
(atomic number: $Xe=54,Ce=58,Eu—63$)

• A. $[Xe]4f^7$ and $[Xe]4f^1$
• B. $[Xe]4f^{7}6s^2$ and $[Xe]4f^{2}6s^2$
• C. $[Xe]4f^2$ and $[Xe]4f^7$
• D. $[Xe]4f^4$ and $[Xe]4f^9$

Answer 1

Answer: (A)

$E{u}_{63}\Rightarrow \left[Xe\right]4f^{7}5d^{\circ }6s^2$
$E{u}^{2\oplus }\Rightarrow \left[Xe\right]4f^7$
$C{e}_{58}\Rightarrow \left[Xe\right]4f^{1}5d^{1}6s^2$
$C{e}^{3\oplus }\Rightarrow \left[Xe\right]4f^1$