Question

What is the electronic configuration of \( \text{Cu} \)?

• A. \( [\text{Ar}] 3d^{10} 4s^1 \)
• B. \( [\text{Ar}] 3d^9 4s^2 \)
• C. \( [\text{Ar}] 3d^{10} 4s^2 \)
• D. \( [\text{Ar}] 3d^9 4s^1 \)

Hint:

Transition elements often show exceptions in electronic configurations to achieve a half-filled or completely filled \( d \)-subshell.

Answer 1

The Correct Option is A

Copper deviates from the expected configuration \( [\text{Ar}] 3d^9 4s^2 \) to achieve greater stability with a completely filled \( 3d \)-subshell. The actual configuration is: \[ [\text{Ar}] 3d^{10} 4s^1. \] This arrangement lowers the energy of the atom due to the enhanced stability of a completely filled \( d \)-subshell. ---
Final Answer: \[ \boxed{[\text{Ar}] 3d^{10} 4s^1} \]