Chapter 10

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Section 10.1

Intermolecular Forces

Intramolecular Bonding

 _{“Within” the molecule.}

 _{Molecules are formed by sharing electrons between}

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Section 10.1

 _{Forces that occur between molecules.}  _{Dipole–dipole forces}

 _{Hydrogen bonding}

 _{London dispersion forces}

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Section 10.1

Intermolecular Forces

Hydrogen Bonding in Water

 _{Blue dotted lines are the intermolecular forces between}

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Section 10.1

Which are stronger, intramolecular bonds or intermolecular forces?

How do you know?

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Section 10.1

Phase Changes

 _{When a substance changes from solid to liquid to}

gas, the molecules remain intact.

 _{The changes in state are due to changes in the}

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Section 10.1

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Section 10.1

Phase Changes

 _{Solid to Liquid}

 _{As energy is added, the motions of the molecules}

increase, and they eventually achieve the greater movement and disorder characteristic of a liquid.

 _{Liquid to Gas}

 _{As more energy is added, the gaseous state is}

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Section 10.1

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Section 10.1

Dipole-Dipole Forces

 _{Dipole moment – molecules with polar bonds often}

behave in an electric field as if they had a center of positive charge and a center of negative charge.

 _{Molecules with dipole moments can attract each}

other electrostatically. They line up so that the

positive and negative ends are close to each other.

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Section 10.1

Dipole-Dipole Forces

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Section 10.1

Hydrogen Bonding

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Section 10.1

Hydrogen Bonding

 _{Strong dipole-dipole forces.}

 _{Hydrogen is bound to a highly electronegative atom}

– nitrogen, oxygen, or fluorine.

 _{That same hydrogen is then electrostatically}

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Section 10.1

London Dispersion Forces

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Section 10.1

London Dispersion Forces

 _{Instantaneous dipole that occurs accidentally in a}

given atom induces a similar dipole in a neighboring atom.

 _{Significant in large atoms/molecules.}

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Section 10.1

Melting and Boiling Points

 _{In general, the stronger the intermolecular forces,}

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Section 10.1

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Section 10.1

Which molecule is capable of forming stronger

intermolecular forces?

N₂ H₂O

Explain.

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Section 10.1

Draw two Lewis structures for the formula C₂H₆O and compare the boiling points of the two

molecules.

C

H

C

H

O H

C

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Section 10.1

Which gas would behave more ideally at the same conditions of P and T?

CO or N₂

Why?

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Section 10.2

The Liquid State

Liquids

 _{Low compressibility, lack of rigidity, and high density}

compared with gases.

 _{Surface tension – resistance of a liquid to an increase in}

its surface area:

 _{Liquids with large intermolecular forces tend to have}

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Section 10.2

The Liquid State

Liquids

 _{Capillary action – spontaneous rising of a liquid in a}

narrow tube:

 _{Cohesive forces – intermolecular forces among the}

molecules of the liquid.

 _{Adhesive forces – forces between the liquid}

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Section 10.2

The Liquid State

 _{Which force dominates alongside the glass tube –}

cohesive or adhesive forces?

cohesive forces

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Section 10.2

The Liquid State

Concave Meniscus Formed by Polar Water

 _{Which force dominates alongside the glass tube –}

cohesive or adhesive forces?

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Section 10.2

The Liquid State

Liquids

 _{Viscosity – measure of a liquid’s resistance to flow:}

 _{Liquids with large intermolecular forces or molecular}

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Section 10.3

An Introduction to Structures and Types of Solids

Solids

 _{Amorphous Solids:}

 _{Disorder in the structures}  _Glass

 _{Crystalline Solids:}

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Section 10.3

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Section 10.3

Bragg Equation

 _{Used to determine the interatomic spacings.}

n = integer

= wavelength of the X rays

d = distance between the atoms

= angle of incidence and reflection = 2 sin

 

n d



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Section 10.3

Bragg Equation

= 2 sin

 

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Section 10.3

Types of Crystalline Solids

 _{Ionic Solids – ions at the points of the lattice that}

describes the structure of the solid.

 _{Molecular Solids – discrete covalently bonded molecules}

at each of its lattice points.

 _{Atomic Solids – atoms at the lattice points that describe}

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Section 10.3

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Section 10.3

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Section 10.4

Structure and Bonding in Metals

Closest Packing Model

 _{Closest Packing:}

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Section 10.4

The Closest Packing Arrangement of Uniform Spheres

 _abab_{packing – the 2}nd_{layer is like the 1}st_{but it is displaced so that}

each sphere in the 2nd_{layer occupies a dimple in the 1}st_layer.

 _{The spheres in the 3}rd_{layer occupy dimples in the 2}nd_{layer so that}

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Section 10.4

The Closest Packing Arrangement of Uniform Spheres

 _abca_{packing – the spheres in the 3}rd_{layer occupy dimples in the}

2nd_{layer so that no spheres in the 3}rd_{layer lie above any in the 1}st

layer.

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Section 10.4

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Section 10.4

Structure and Bonding in Metals

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Section 10.4

The Indicated Sphere Has 12 Nearest Neighbors

 _{Each sphere in both ccp}

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Section 10.4

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Section 10.4

Determine the number of metal atoms in a unit cell if the packing is:

a) Simple cubic

b) Cubic closest packing

a) 1 metal atom

b) 4 metal atoms

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Section 10.4

A metal crystallizes in a face-centered cubic structure.

Determine the relationship between the radius of the metal atom and the length of an edge of the unit cell.

Length of edge = r  8

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Section 10.4

Silver metal crystallizes in a cubic closest packed

structure. The face centered cubic unit cell edge is 409 pm.

Calculate the density of the silver metal.

Density = 10.5 g/cm

3 CONCEPT CHECK!

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Section 10.4

Bonding Models for Metals

 _{Electron Sea Model}

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Section 10.4

The Electron Sea Model

 _{A regular array of cations in a “sea” of mobile valence}

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Section 10.4

Band or Molecular Orbital (MO) Model



Electrons are assumed to travel around the metal

crystal in molecular orbitals formed from the

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Section 10.4

Molecular Orbital Energy Levels Produced When

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Section 10.4

The Band Model for Magnesium

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Section 10.4

Metal Alloys

 _{Substitutional Alloy – some of the host metal atoms are}

replaced by other metal atoms of similar size.

 _{Interstitial Alloy – some of the holes in the closest}

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Section 10.4

Two Types of Alloys

 _{Brass is a substitutional}

alloy.

 _{Steel is an interstitial}

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Section 10.5

Carbon and Silicon: Network Atomic Solids

Network Solids

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Section 10.5

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Section 10.5

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Section 10.5

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Section 10.5

Ceramics

 _{Typically made from clays (which contain silicates) and}

hardened by firing at high temperatures.

 _{Nonmetallic materials that are strong, brittle, and}

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Section 10.5

Semiconductors

 _{n-type semiconductor – substance whose conductivity is}

increased by doping it with atoms having more valence electrons than the atoms in the host crystal.

 _{p-type semiconductor – substance whose conductivity is}

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Section 10.5

Energy Level Diagrams for

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Section 10.5

Silicon Crystal Doped with

(a) Arsenic and

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Section 10.6

Molecular Solids

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Section 10.7

Ionic Solids

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Section 10.7

Ionic Solids

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Section 10.7

Ionic Solids

Three Types of Holes in Closest Packed Structures

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Section 10.7

Ionic Solids

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Section 10.7

Ionic Solids

3) Octahedral holes are formed between two sets of three spheres in adjoining layers of the closest packed

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Section 10.7

Ionic Solids

 _{For spheres of a given diameter, the holes increase in}

size in the order:

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Section 10.7

Ionic Solids

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Section 10.8

Vapor Pressure and Changes of State

Behavior of a Liquid in a Closed Container

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Section 10.8

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Section 10.8

Vapor Pressure

 _{Pressure of the vapor present at equilibrium.}

 _{The system is at equilibrium when no net change occurs}

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Section 10.8

What is the vapor pressure of water at 100°C? How do you know?

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Section 10.8

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Section 10.8

Vapor Pressure

 _{Liquids in which the intermolecular forces are large have}

relatively low vapor pressures.

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Section 10.8

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Section 10.8

Clausius–Clapeyron Equation

P_vap = vapor pressure

ΔH_vap = enthalpy of vaporization

R = 8.3145 J/K·mol

T = temperature (in kelvin)

1

2

vap, _vap

vap, 2 1

1 1

ln__ __ =  _  _

 

T

P _H

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Section 10.8

The vapor pressure of water at 25°C is 23.8 torr, and

the heat of vaporization of water at 25°C is 43.9 kJ/mol. Calculate the vapor pressure of water at 65°C.

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Section 10.8

Changes of State

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Section 10.8

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Section 10.8

Which would you predict should be larger for a given substance: ΔH_vap or ΔH_fus?

Explain why.

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Section 10.9

Phase Diagrams

 _{A convenient way of representing the phases of a}

substance as a function of temperature and pressure:

 _{Triple point}  _{Critical point}

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Section 10.9

Phase Diagrams

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Section 10.9

Phase Diagrams

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Section 10.9

Phase Diagrams

As intermolecular forces

increase

, what happens to

each of the following? Why?

_{Boiling point} _Viscosity

_{Surface tension} _{Enthalpy of fusion} _{Freezing point}

_{Vapor pressure}

_{Heat of vaporization}