Network former and breaker oxides

It must also be understood that the bonding between cations and anions in acidic oxides like SiO₂ and is strong, and these simple ions group to form complex ions as   and . In slags, these tend to form hexagonal network. These oxides are, therefore, called network formers or acids. These acidic oxides can accept one or several oxygen ions.

Basic oxides like CaO, MgO, FeO dissociate and form simple ions like  and. All basic oxides are donors of oxygen ions. These oxides are called network breakers, since they destroy the hexagonal network of silica by reacting with it.

Structure of slag

Most slags are silicates. Pure silica has very high viscosity at the melting point. Addition of basic oxides decreases the viscosity by breaking the hexagonal network of silica. Consider the addition of CaO to molten silica. Calcium oxide dissociates to