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# The electronic configuration of divalent cation of Eu is

$(a)\;4f^6\qquad(b)\;4f^7\qquad(c)\;5f^7\qquad(d)\;5f^8$

Answer: $[Xe]4f^7$
The electronic confuguration of Europium is $[Xe]4f^76s^2 \rightarrow$ for its divalent cation, you lose the $6s^2 \rightarrow [Xe]4f^7$
The +2 state has an electron configuration $4f^7$ because the half-filled f-shell gives more stability.