Question

Why do some elements have more than one valency ?

Answer 1

Sometimes, the same element may exhibit one valency in one compound and another valency in other compound. This property is called as variable 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.

The reason behind Why they lose this extra electron is purely a matter of

• the specific element,
• what electron shell they are losing/gaining electrons in,
• and their relative energies to the previous/ next electron shell.
• Also their ability to share electrons between these shells

This will be much more clear once you enter higher standards.