Solid Substances: Solid Substances: Ionic ions, ionic bond molecular molecules, intermolecular bonds metallic atoms, metallic bond macromolecular atoms, covalent bond Structural units held together by attractive forces enough to make a rigid structure silicon, hydrogen, lithium Arrange in terms of M.P. (lowest to highest,1-3) ethanol, methane, dichlorofloromethane, magnesium sulfate Which, if any of these, will dissolve in H 2 O? (*) Underline any of these that dissolve in water and produce a conductive solution? * * * ______________________________ (nonmetal) (metal)

sodium “sea of electrons” model (loosely held negative electrons enveloping the positive cores) Existing in a large number of molecular orbitals (a“conduction band” available to these “mobile electrons”) Delocalization!

Metallic Atoms Metallic Bond Atoms Metallic Bond Type of solid Structural Unit Bond Type Fairly high melting pointsFairly high melting points Exhibits conductivity in molten stateExhibits conductivity in molten state Exhibits conductivity in solid stateExhibits conductivity in solid state Generally insoluble in water and other solventsGenerally insoluble in water and other solvents

Ionic Ions Ionic Bond Ions Ionic Bond Type of solid Structural Unit Bond Type High melting pointsHigh melting points Exhibits conductivity when moltenExhibits conductivity when molten Nonconductive in solid stateNonconductive in solid state Often soluble in waterOften soluble in water Aqueous solutions are conductiveAqueous solutions are conductive

Molecular Molecules Intermolecular Bonds Bonds Type of solid Structural Unit Bond Type Low melting pointsLow melting points Generally nonconductive when moltenGenerally nonconductive when molten Nonconductive in solid stateNonconductive in solid state Solubility depends on solventSolubility depends on solvent Aqueous solutions generally not conductiveAqueous solutions generally not conductive

Macromolecular atoms covalent atoms covalent Type of solid Structural Unit Bond Type High melting pointsHigh melting points Nonconductive when moltenNonconductive when molten Nonconductive in solid stateNonconductive in solid state InsolubleInsoluble