This episode classifies compounds into three types based on their chemical bonds: ionic, covalent, and metallic. Ionic compounds, formed by electron transfer, are brittle with high melting points and conduct electricity when molten. Covalent compounds, formed by electron sharing, have lower melting points and poor conductivity, with the exception of network covalent materials. Metallic compounds, with their "sea" of electrons, are conductive, malleable, and have high melting points. It explains how the electronegativity difference between atoms can be used to predict the type of bonding and resulting properties.