# Question #09d7f

Aug 17, 2017

Copper has two oxidation states because it can lose either one or two valence electrons.

#### Explanation:

Copper has a valence electron configuration of ${\text{4s"^1 "3d}}^{10}$.

The $\text{4s}$ and $\text{3d}$ levels are very close in energy, so copper can lose one or two electrons.

In copper(II), copper loses two electrons, leaving ${\text{3d}}^{9}$.

In copper(I), copper loses its $\text{4s}$ electron. This gives a valence configuration of ${\text{3d}}^{10}$.

The ${\text{3d}}^{10}$ configuration is somewhat stable as it is a filled subshell.