What is the electronic configuration: Cu2+(Z=29) of least position?

Question

What is the electronic configuration: Cu2+(Z=29) of least position? (A)  [Ar]4s1,3d8  (B)  [Ar]4s2,3d10,4p1  (C)  [Ar]4s1,3d10  (D)  [Ar]3d9

Tardigrade Admin · Accepted Answer

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 +} = 18 electrons 1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}, 3 d^{9}

∵

_{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}

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