Question

What is the electronic configuration: $ Cu^{2+}(Z=29) $ of least position?

• A. $ [Ar]4s^{1},3d^{8} $
• B. $ [Ar]4s^{2},3d^{10},4p^{1} $
• C. $ [Ar]4s^{1},3d^{10} $
• D. $ [Ar]3d^{9}$

Answer 1

Answer: (D)

According to aufbau principle electronic configuration of $C u(29)$ should be
$29 C u=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6} 3 d^{9}, 4 s^{2}$
But correct electronic configuration of $C u$ is
${ }_{29} C u=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6} 3 d^{10}, 4 s^{1} $
$C u^{2+}=\underbrace{1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}}_{18 \text { electrons }}, 3 d^{9}$
$ \because$ ${ }_{18} A r=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}$
So, ${ }_{29} C u^{2+}=[A r] 3 d^{9}$