13Intermolecular 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 • H O 2 • C2H5OH • CO2 • C6H12O6 • CH 4 • The alkanes, alkenes, etc. • NH 3 • The diatomic molecules • NO 2 • The noble gases • CO

• C2H6 Metals

• A lattice of positive ions in a “sea of electrons” • Metal atoms have low electronegativity Metal Examples

• Pb • Brass (Cu + Zn) • Ag • Bronze (Cu + Sn) • Au • Stainless Steel (Fe/Cr/C) • Cu • Zn • Fe Ionic Solids

• A lattice of positive and negative ions Ionic Solid Examples

• NaCl • CaCl2

• KCl • MgSO4

• KI • Fe2O3

• FeCl3 • AgNO3

• CaCO3 • + 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)