The electron configuration of copper (Cu) is [Ar] 3d¹⁰ 4s².
To understand this electron configuration, let's break it down:
[Ar] represents the electron configuration of the noble gas argon (atomic number 18). It signifies that the 18 electrons of argon fill up the inner electron shells before copper's configuration.
3d¹⁰ refers to the filling of the 3d subshell. The "3d" indicates that the electrons are in the third energy level (n = 3) and the "¹⁰" signifies that there are ten electrons occupying the 3d orbitals. This configuration fills up the 3d subshell completely.
4s² represents the filling of the 4s subshell. The "4s" indicates that the electrons are in the fourth energy level (n = 4), and the "²" signifies that there are two electrons in the 4s orbital.
The electron configuration of copper, [Ar] 3d¹⁰ 4s², shows that copper has a total of 29 electrons. The completely filled 3d subshell contributes to the unique properties of copper and other transition metals.