Which of the following electron configurations is correct for copper, (atomic number 29)?

Options

A. `[Ar] 3d^(10) 4s^1`
B. `[Kr] 3d^9 4s^1`
C. `[Ar] 3d^9 4s^2`
D. `[Kr] 3d^(10) 4s^1`

Answer

A