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

The Correct Option is A

$Eu_{63} \Rightarrow\, \left[Xe\right] 4 f^{7} 5 d^{\circ} 6s^{2}$ $Eu^{2\oplus} \Rightarrow \left[Xe\right]4f^{7}$ $Ce_{58} \Rightarrow\left[Xe\right]4 f^{1} 5d^{1} 6s^{2}$ $Ce^{3\oplus} \Rightarrow\, \left[Xe\right]4f^{1}$