Intermolecular Forces andIntermolecular Forces andPhysical PropertiesPhysical Properties

ChemistryChemistry

Unit 6Unit 6

Non-Polar Covalent CompoundsNon-Polar Covalent Compounds

ExamplesExamples:: O O22, CH, CH44, CO, CO22

Types of particles:Types of particles: 2 or more non-metals 2 or more non-metals

IMF’sIMF’s = Dispersion = Dispersion

Physical statePhysical state – can be s, l, or g – – can be s, l, or g – depends on molecular weight (MW)depends on molecular weight (MW)

Melting/Boiling PtsMelting/Boiling Pts. – very low to low. – very low to low

Solubility in waterSolubility in water – Not soluble – Not soluble

ConductivityConductivity – poor to non conducting. – poor to non conducting.

Polar Covalent CompoundsPolar Covalent CompoundsExamplesExamples: H: H22S, HCl, HS, HCl, H22OO

Types of particlesTypes of particles: usually 2 or more non-: usually 2 or more non-metalsmetals

IMF’sIMF’s = Dipole-Dipole and maybe hydrogen = Dipole-Dipole and maybe hydrogen bondsbonds

Physical statePhysical state – can be s, l, or g – depends on – can be s, l, or g – depends on molecular weight (MW)molecular weight (MW)

Melting/Boiling PtsMelting/Boiling Pts. – low to medium. – low to medium

Solubility in waterSolubility in water – most are soluble – most are soluble

ConductivityConductivity – Do not conduct. – Do not conduct.

Ionic CompoundsIonic Compounds

ExamplesExamples: NaCl, MgO: NaCl, MgOTypes of particlesTypes of particles: Metal and Non-metal: Metal and Non-metalIMF’sIMF’s = Ionic bonds = Ionic bondsPhysical statePhysical state – crystalline solids, brittle – crystalline solids, brittleMelting/Boiling Pts.Melting/Boiling Pts. – very high – very highSolubility in waterSolubility in water – most are soluble – most are solubleConductivityConductivity – conduct as liquids or when – conduct as liquids or when dissolved in water..dissolved in water..

MetallicMetallic

ExamplesExamples: Al, Cu, Fe: Al, Cu, Fe

Types of particlesTypes of particles: cations in sea of electrons: cations in sea of electrons

IMF’sIMF’s = metallic bonds = metallic bonds

Physical statePhysical state – all solids except Hg – all solids except Hg

Melting/Boiling Pts.Melting/Boiling Pts. – variable – depends on – variable – depends on charge and sizecharge and size

Solubility in waterSolubility in water – Not soluble – Not soluble

ConductivityConductivity – conduct as solids or liquids – conduct as solids or liquids

Covalent Network CompoundsCovalent Network CompoundsSome covalently bonded substances DO NOT form discrete molecules.

Diamond, a network of covalently bonded carbon atoms

Graphite, a network of covalently bonded carbon atoms

Network Covalent SolidsNetwork Covalent SolidsNetwork solidsNetwork solids – solids in which – solids in which all the atomsall the atoms are covalently are covalently bonded to bonded to each othereach otherNetwork solids melt at very high Network solids melt at very high temperatures, or not at all temperatures, or not at all (decomposes)(decomposes)

– Diamond does not really melt, but Diamond does not really melt, but vaporizes to a gas at 3500 vaporizes to a gas at 3500 ooC and C and beyondbeyond

– SiC, used in grinding, has a melting SiC, used in grinding, has a melting point of about 2700 point of about 2700 ooC C

Network CovalentNetwork Covalent

ExamplesExamples: Carbon, Silicon, SiO: Carbon, Silicon, SiO22, C, C6060

Types of particlesTypes of particles: usually single atoms: usually single atoms

IMF’sIMF’s = covalent bonds = covalent bonds

Physical statePhysical state – solids – solids

Melting/Boiling PtsMelting/Boiling Pts. – very high. – very high

Solubility in waterSolubility in water – Not soluble – Not soluble

Conductivity Conductivity – poor to non conducting.– poor to non conducting.

Diamond vs. GraphiteDiamond vs. GraphiteDifferent properties due to how it is bonded.Different properties due to how it is bonded.

Diamond – very hard, high mp- carbons 4 bonds Diamond – very hard, high mp- carbons 4 bonds eacheach

Graphite – soft solid –carbons have 3 bondsGraphite – soft solid –carbons have 3 bonds

BuckyBalls – CBuckyBalls – C6060

Allotropes of CarbonAllotropes of Carbon

Allotropes of carbon Link

Types of Molecular SolidsTypes of Molecular Solids

CovalentMolecular

(H2O)

CovalentNetwork

(SiO2 - quartz)

Amorphous(SiO2 - glass)