MCQ
Which of the following options does not represent ground state electronic configuration of an atom?
  • A
    $\ce{1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^8 4 s^2} $
  • B
    $\ce{1 s^2 2 p^6 3 s^2 3 p^6 3 d^9 4 s^2 }$
  • C
    $\ce{ 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^{10} 4 s^1} $
  • $\ce{1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^5 4 s^1}$

Answer

Correct option: D.
$\ce{1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^5 4 s^1}$
Correct configuration should be $\ce{1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^{10} 4 s^1}$ for the copper which has atomic number $\ce{29(29Cu)}$. Due to extra stability of full filled orbital of $d-$ subshell, the last electron enter into $d-$ orbital instead of $s-$ orbital.

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