The valency of copper (Cu) can vary depending on the compound or context in which it is found. Copper is a transition metal and can exhibit different oxidation states or valencies.
The most common oxidation states for copper are +1 and +2. In the +1 oxidation state, copper loses one electron to achieve a stable electron configuration, resulting in a valency of +1. In the +2 oxidation state, copper loses two electrons, leading to a valency of +2.
For example, in copper(I) compounds, such as copper(I) oxide (Cu2O) or cuprous chloride (CuCl), copper has a valency of +1. In copper(II) compounds, such as copper(II) sulfate (CuSO4) or copper(II) chloride (CuCl2), copper has a valency of +2.
However, it's important to note that copper can also exhibit other oxidation states, such as +3 in certain compounds. So, the valency of copper can vary depending on the specific compound or chemical context.