Properties of Substances

Ionic substances

form crystals (lattice of positive and negative ions); high melting and boiling points; hard; brittle; conduct electricity when dissolved and when molten (melted); good insulators as solid

Covalent Compounds

Low melting and boiling points (many are liquid or gases at room temp); soft or brittle solid forms; poor electrical and thermal conductivity

Metallic

shiny (luster); malleable and ductile; conduct heat and electricity; metallic oxides are basic and ionic; lose electrons to form cations

Crystalline Solids (include reasons)

low vapor pressure and low volatility (strong Coulombic force of attraction); high melting and boiling points (strong Coulombic force of attraction); brittle (like—charges repel each other when layers slide over one another); conduct electricity when molten or dissociated (ions must be free to move); dissolves and dissociates in water (polar water molecules attach to charged ions)