The electron configuration of copper (Cu) is [Ar] 3d¹⁰ 4s¹.
To understand this configuration, let's break it down:
[Ar]: Represents the electron configuration of the noble gas argon (1s² 2s² 2p⁶ 3s² 3p⁶). The noble gas configuration is used as a shorthand notation to indicate the filled inner electron shells prior to the outermost electron shell.
3d¹⁰: Refers to the 3d orbital, which can hold a maximum of 10 electrons. In the case of copper, all 10 possible slots in the 3d orbital are filled, resulting in a completely filled 3d subshell.
4s¹: Represents the 4s orbital, which can accommodate a maximum of 2 electrons. In copper's case, only 1 electron occupies the 4s orbital.
So, the electron configuration of copper is [Ar] 3d¹⁰ 4s¹, indicating that it has a filled 3d subshell with 10 electrons and 1 electron in the 4s orbital.