We know that s orbital can accommodate a maximum of 2 electrons and d orbital can accommodate a maximum of 10 electrons. The atomic number of copper is 29. because half filled and fully filled subshells have extra Stability.

Why does copper have valency 1 and 2?

Solution: When an element does not have a specific valency, its valency is called variable valency. Copper has valency ‘1’ and ‘2’ that is the number of electrons lost or gained is 1 or 2 in different compounds..

Why does copper have a variable valency?

Copper shows variable valency because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell that is loss from the penultimate shell and hence exhibit more than one valency.

Some elements show variable valency because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency. This is termed variable valency.