Question

Which of the following best describes why [Ar]4s13d10 is the best electron configuration for copper (Cu), instead of [Ar]4s23d9?

A) A completely filled d shell is appreciably more stable than the latter configuration
B) A completely filled s shell is unstable
C) It is easier to fill the following p orbitals
D) None of the above are correct

Answer 1

Copper's electron configuration is [Ar]4s1d10 because a completely filled d shell is more stable, which results in lower overall energy for the atom.

Step-by-step explanation:

The electron configuration for copper that best describes its stability is [Ar]4s13d10 rather than [Ar]4s23d9. The best description for this preference is that a completely filled d shell is more stable than the latter configuration (Option A). Half-filled and completely filled subshells represent conditions of preferred stability, leading to an energetically more favorable state. The stability gained by having a filled 3d subshell outweighs the energy required to move an electron from the 4s to 3d orbital.