why are covalent network substances brittle
Because the electrons in ionic solids are localized (in the ions) these solids tend to be stiff and brittle like covalent solids. As solids they do not conduct electricity (again because of the localize electrons).However, they do conduct electricity as liquids (or when dissolved in water) since then the ions can move.istortion away from this geometry can only occur through a breaking of covalent sigma bonds. As a result, the melting point of covalent solids is extremely high. They also tend to be extremely hard substances that will break into pieces rather than smoothly change shape. We say that they are stiff and brittle.