* Valence refers to the combining capacity of an element. Silicon (Si) has a valence of +4, meaning it can form four bonds. Oxygen (O) has a valence of -2, meaning it can form two bonds.
* In a compound, the valences of the elements combine to create a neutral molecule. In SiO₂, the +4 valence of silicon balances out the -4 total valence of the two oxygen atoms.
Therefore, instead of a single valence number, we talk about the valences of the individual elements within the compound.
