13Intermolecular Forces, Liquids, and Solids

The four types of solids

Intermolecular Forces of Attraction

• Ch 12 was all about gases… particles that don’t attract each other.

Intermolecular Forces of Attraction

• Ch 13 is about liquids and solids… where the attraction between particles allows the formation of solids and liquids.

Intermolecular Forces of Attraction

• These attractions are called “intermolcular

forces of attractions” or IMF’s for short.

• Intermolcular forces vs intramolecular forces

Four Solids – Overview

• Molecular Solids (particles with IMF’s)

• Metals (metallic bonding)

• Ionic Solids (ionic bonding)

• Covalent Network Solids (covalent bonding)

Molecular Solids

• Molecules or noble gases (individual particles)

Molecular Solid Examples • H2O

• CO2

• CH4

• NH3

• NO2

• CO

• C2H6

• C2H5OH

• C6H12O6

• The alkanes, alkenes, etc.

• The diatomic molecules

• The noble gases

Metals

• A lattice of positive ions in a “sea of electrons”

• Metal atoms have low electronegativity

Metal Examples

• Pb

• Ag

• Au

• Cu

• Zn

• Fe

• Brass (Cu + Zn)

• Bronze (Cu + Sn)

• Stainless Steel (Fe/Cr/C)

Ionic Solids

• A lattice of positive and negative ions

Ionic Solid Examples

• NaCl

• KCl

• KI

• FeCl3

• CaCO3

• CaCl2

• MgSO4

• Fe2O3

• AgNO3

• + ion & - ion

Covalent Network Solids

• Crystal held together with covalent bonds

Covalent Network Solid Examples

• C(diamond)

• C(graphite)

• SiO2 (quartz, sand, glass)

• SiC

• Si

• WC

• BN

Properties of

Metals

Metals are good

conductors of heat and

electricity.

They are shiny and

lustrous.

Metals can be pounded

into thin sheets

(malleable) and drawn

into wires (ductile).

Metals do not hold onto

their valence electrons

very well. They have low

electronegativity.

Properties of Ionic Solids

• Brittle

• High MP & BP

• Dissolves in H2O

• Conducts as

(l), (aq), (g)

Electrical Conductivity

Intermolecular Forces (IMFs)

• Each intermolecular force involves + and –

attractions.

• The list from weakest to strongest is:

– London Dispersion Forces

– Dipole-dipole interactions

– Hydrogen bonding

– Ion-Ion Interactions

Ion-Ion Interaction

• + ion attracts a – ion (opposites attract)

• Lattice energy is a measure of the

strength of this interaction

• NaCl(s) + energy Na+(g) + Cl-(g)

Dipole-Dipole Interaction

• Same idea as ion-ion interaction, but not

as strong because the charges are only

“partial charges”.

• Polar molecules have this kind of IMF.

Hydrogen Bonding

• This is a special case of dipole-dipole

interaction (about 10x stronger).

• H-O, H-F, H-N

– Atoms are small and electronegative

– Very polar bond leads to stronger IMF

London Dispersion Forces

London Dispersion Forces

• Every atom attracts every other atom with

this force. (H-bonding & LDF, Dipole & LDF)

• +/- attraction again but the polarity is only

temporary.

• LDF is stronger with a “more polarizable

electron cloud”. (use these words in FRQ)

– More electrons

– Larger atoms or longer molecules

Examples to Recognize

• London dispersion forces – non-polar

molecules and other molecules, too.

• Dipole-dipole interactions – polar

molecules.

• Hydrogen bonding – polar molecules with

– H-O (water, alcohols, oxoacids)

– H-N (ammonia, amines)

– H-F (HF)