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Chemistry · PYQ NEET UG 2016(1)
हिन्दीThe electronic configurations of Eu (atomic no. 63), Gd (atomic no. 64) and Tb (atomic no. 65) are ______ respectively.
Correct answer · Option 4
\( [\text{Xe}] 4f^7 6s^2 \), \( [\text{Xe}] 4f^7 5d^1 6s^2 \) and \( [\text{Xe}] 4f^9 6s^2 \)
Explanation
Standard lanthanide configurations: Eu (63) is \( [\text{Xe}] 4f^7 6s^2 \), Gd (64) is \( [\text{Xe}] 4f^7 5d^1 6s^2 \) due to extra stability of half-filled f-subshell, and Tb (65) is \( [\text{Xe}] 4f^9 6s^2 \).
