Intermolecular Forces and Physical Properties Chemistry Unit 6

Non-Polar Covalent Compounds Examples: O 2, CH 4, CO 2 Types of particles: 2 or more non-metals IMF’s = Dispersion Physical state – can be s, l, or g – depends on molecular weight (MW) Melting/Boiling Pts. – very low to low Solubility in water – Not soluble Conductivity – poor to non conducting.

Polar Covalent Compounds Examples: H 2 S, HCl, H 2 O Types of particles: usually 2 or more non- metals IMF’s = Dipole-Dipole and maybe hydrogen bonds Physical state – can be s, l, or g – depends on molecular weight (MW) Melting/Boiling Pts. – low to medium Solubility in water – most are soluble Conductivity – Do not conduct.

Ionic Compounds Examples: NaCl, MgO Types of particles: Metal and Non-metal IMF’s = Ionic bonds Physical state – crystalline solids, brittle Melting/Boiling Pts. – very high Solubility in water – most are soluble Conductivity – conduct as liquids or when dissolved in water..

Metallic Examples: Al, Cu, Fe Types of particles: cations in sea of electrons IMF’s = metallic bonds Physical state – all solids except Hg Melting/Boiling Pts. – variable – depends on charge and size Solubility in water – Not soluble Conductivity – conduct as solids or liquids

Covalent Network Compounds Some 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 Solids Network solids – solids in which all the atoms are covalently bonded to each other Network solids melt at very high temperatures, or not at all (decomposes) –Diamond does not really melt, but vaporizes to a gas at 3500 o C and beyond –SiC, used in grinding, has a melting point of about 2700 o C

Network Covalent Examples: Carbon, Silicon, SiO 2, C 60 Types of particles: usually single atoms IMF’s = covalent bonds Physical state – solids Melting/Boiling Pts. – very high Solubility in water – Not soluble Conductivity – poor to non conducting.

Diamond vs. Graphite Different properties due to how it is bonded. Diamond – very hard, high mp- carbons 4 bonds each Graphite – soft solid –carbons have 3 bonds

BuckyBalls – C 60

Allotropes of Carbon Allotropes of carbon Link Allotropes of carbon Link

Types of Molecular Solids Covalent Molecular (H 2 O) Covalent Network (SiO 2 - quartz) Amorphous (SiO 2 - glass)