text: COVALENT\nValence electrons are shared between adjacent atoms.  \nHighly directional bonds produce molecules rather than crystals.\nAlmost all polymers exhibit this, as do diamond and silicon carbide (unusual ceramics).\n\nIONIC\nMetallic element gives up valence electrons to nonmetallic element.\nTends to produce the crystalline structures we call ceramics.\nVery strong bonds --> high melting points, elastic moduli.\nImparts hardness, brittleness and insulativity.\n\nMETALLIC\nInvolves “free-roaming” valence electrons.\nTends to produce the crystalline structures we call metals.\nImparts conductivity, ductility/malleability, opacity and reflectivity.