The electronic configuration of Eu (Atomic No. 63), Gd (Atomic No. 64) and Tb (Atomic No. 65) are:

Options

A. `[Xe] 4f^(7) 6s^(2), [Xe] 4 f^(7) 5d^(1) 6s^(2)` and `[Xe] f^(9) 6s^(2)`
B. `[Xe] 4f^(7) 6s^(2), [Xe] 4f^(8) 6s^(2)` and `[Xe] 4f^(8) 5 d^(1) 6s^(2)`
C. `[Xe] 4f^(6) 5 d^(1) 6 s^(2), [Xe] 4 f^(8) 6 s^(2)` and `[Xe] 4f^(8) 5 d^(1) 6s^(2)`
D. `[Xe] 4f^(8) 5 d^(1) 6 s^(2)`

Answer

A

Explanation

`._(63)Eu - gt [Xe] 4f^(7) 6 s^(2)`
`._(64)Gd rarr [Xe] 4f^(7) 5 d^(1) 6 s^(2)`
`._(65)Tb rarr [Xe] 4f^(9) 5 d^(0) 6 s^(2)`