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

Options

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

Answer

B

Explanation

Refer to footnote on page `3//14` the electronic configuration of Eu (Z= 63) ,Gd (Z= 64) and Tb (Z=65) are respectively :
`[Xe] 4f^(7) 6s^(2) [Xe] 4f^(7) 5d^(1) 6s^(2)` and `[Xe] 4f^(9) 6s^(2)`
Thus , option ( b) is correct.