Chemistry

Question Analysis
This question tests the student's understanding of the electron configuration of a copper ion (Cu²⁺) and the order of electron loss from the 4s and 3d sublevels.

Key Concept Explanation
The electron configuration of a neutral copper atom is [Ar] 4s¹ 3d¹⁰. When forming Cu²⁺, the 4s electron is lost first, followed by one 3d electron, resulting in the configuration [Ar] 3d⁹.

Step-by-step Solution
1. Determine the electron configuration of a neutral copper atom: [Ar] 4s¹ 3d¹⁰.
2. Remove the 4s electron first: [Ar] 3d¹⁰.
3. Remove one 3d electron: [Ar] 3d⁹....