chapter 12 modern materials - learning.hccs.edu

Chapter 12

Solids and Modern Materials

1

CLASSIFICATION OF SOLIDS

2

Classifying Solids Based on Bonds

© 2015 Pearson Education, Inc.3

Metallic solids collectively

shared electrons

Ionic solids composed of

cations and anions

Covalent-network solids

network of covalent bondsMolecular solids molecules

joined by weak forces

Two Other Types of Solids

Polymers

Long chains of atoms connected

by covalent bonds

Different properties than small

molecules or metallic or ionic

compounds

Nanomaterials

Compounds with crystals on the

order of 1–100 nm

Very different properties than

larger crystalline materials

4http://4.bp.blogspot.com/-sGHAta2TI2w/Tf9CqTad5hI/AAAAAAAAACE/90tg02_s330/s1600/Polymer.gif http://discovermagazine.com/~/media/Images/Issues/2016/JanFeb/buckyball.jpg

Two Other Types of Solids

Polymers

Long chains of atoms connected

by covalent bonds

Different properties than small

molecules or metallic or ionic

compounds

Nanomaterials

Compounds with crystals on the

order of 1–100 nm

Very different properties than

larger crystalline materials

5http://4.bp.blogspot.com/-sGHAta2TI2w/Tf9CqTad5hI/AAAAAAAAACE/90tg02_s330/s1600/Polymer.gif http://www.photonics.com/Article.aspx?AID=41439

Gold nanocages of different wall

thickness and pore size of walls

STRUCTURES OF SOLID

6

Structures of Solids

• Crystalline solids

– Regular repeating

pattern of atoms

7

• Amorphous

– Lack order in atom’s

arrangement

https://opentextbc.ca/chemistry/wp-content/uploads/sites/150/2016/05/CNX_Chem_10_05_TypesSol.jpg

Chemists are interested in crystalline solids because

of their regular pattern

What causes the repeating pattern in

crystals?

The unit cell

8

Unit Cell

• Unit cell

– Smallest repeating

portion of a crystal

• Structure of crystal

defined by

– Size and shape of

the unit cell

– Atoms within the

unit cell9

http://www.ck12.org/Chemistry/Unit-Cells/lesson/Unit-Cells-CHEM/

Lattice Points

• Lattice points

– Define structure of

the crystal

– Environments are

identical

• Lattice vectors

– Connect the points

– Define the unit cell

10

Lattice

Point

http://www.ck12.org/Chemistry/Unit-Cells/lesson/Unit-Cells-CHEM/

2-D Lattices

11

• Five two-dimensional lattices:

© 2015 Pearson Education, Inc.

3-D Crystal Lattices

• Seven basic three-dimensional lattices:

12© 2015 Pearson Education, Inc.

Lattices: Primitive or Centered

• Primitive lattices

– Atoms only in

lattice points

13

• Centered lattices

– Atoms not restricted to lattice

points

– Body-center

• Atom in center of cell

– Face-center

• Atom in center of face© 2015 Pearson Education, Inc.

Lattices: Motifs• Motif

– Small group of atoms

– Associated with lattice point

– Structure follows unit cell

– Bonds can form across unit cells


An important difference

between crystalline solids and

amorphous solids is that

crystalline solids have

a. flat surfaces.

b. variable colors.

c. repeating lattice patterns.

d. low melting points.

15

An important difference

between crystalline solids and

amorphous solids is that

crystalline solids have

a. flat surfaces.

b. variable colors.

c. repeating lattice patterns.

d. low melting points.

16

METALLIC SOLIDS

17

Metallic Structure: Metals• Three structure types of many metals


Metallic Structure: Close Packing

• Atoms pack as close

as possible

• Two common types

of packing

Cubic close-packed

Hexagonal close-

packed


Alloys• Alloys

– Contain more than one element

– Characteristic properties of metals

– Used to change the properties of certain metals


Types of Alloys

• Solid solutions (homogeneous mixtures)

– Substitutional alloys:

• Second element takes the place of a metal atom

– Interstitial alloys:

• Second element fills a space in the lattice of metal atoms

• Heterogeneous alloys:

– Components not dispersed uniformly24


Types of Alloys

• Intermetallic Compounds

– Compounds, not mixtures

– Atoms ordered, not randomly distributed

– Distinct properties, definite composition


In an interstitial alloy, the

solute radii are _______ the

solvent radii.

a. greater than

b. equal to

c. less than

d. sequestered by

26

In an interstitial alloy, the

solute radii are _______ the

solvent radii.

a. greater than

b. equal to

c. less than

d. sequestered by

27

METALLIC BONDING

28

Metallic Bonding

• Metallic Bonding

– Delocalized electrons

– Explains

• Electrical

conductivity

• Thermal

conductivity

• Ductility

• Malleability


A Molecular-Orbital Approach

• Number of atoms increases, energy gap

decreases

• Approach only takes into account s-orbital30


MO Approach with More Orbitals

• MO with d and p orbitals

– Lead to more bands

– Better explain properties of metals31


IONIC SOLIDS

32

Ionic Solids

• Ionic solids

– Lattice

alternately

charged ions

– Very high melting

and boiling

points

– Electrons

localized

• Brittle

• Electrical

insulators


Ionic Solids• Three

common structures for 1:1 salts

• Most favorable structures – Cation–anion

distances as close as possible

– Anion–anion and cation–cation distances maximized


Ionic Solids

• Most

favorable

structure

depends

mostly

on

– Size of

ions


Effect of Ion Size on Structure

• Most

favorable

structure

depends

mostly

on

– Size of

ions

– Stoichio

metry


The explanation for the

differences in properties

between ionic and metallic

solids is that ___.

a. ionic solids are often water soluble.

b. electrons can move freely in metals,

but not in ionic compounds.

c. the nuclei are in a fixed position in ionic

solids, but not in metals.

d. None of these is correct.37

The explanation for the

differences in properties

between ionic and metallic

solids is that ___.

a. ionic solids are often water soluble.

b. electrons can move freely in metals,

but not in ionic compounds.

c. the nuclei are in a fixed position in ionic

solids, but not in metals.

d. None of these is correct.38

MOLECULAR SOLIDS

39

Molecular Solids

• Molecular Solids

– Atoms or molecules held together intermolecular forces

– Shape (ability to stack) also determines some physical

properties


COVALENT-NETWORK

SOLIDS

41

Covalent-Network Solids

• Covalent-network

solids

– Atoms are covalently

bonded over large

distances

– Higher melting and

boiling points than

molecular solids


Semiconductors

• Semiconductors

– Contain gap between

the occupied and

unoccupied MOs

– Electrons must enter

the conduction band

for electron transfer

– Conduct electricity

sometimes

– Elements IVA gaps

between of 0.08 to

3.05 eV (7 to 300

kJ/mol)

Note: Band gaps over

3.5 eV form insulators


What Forms a Semiconductor?

• Only elements IVA are semiconductors

• Average of 4 valence electrons in inorganic

semiconductors

– GaAs - 3 for Ga, 5 for As


• Doping

– Adding impurity

to a compound

– Changes

conductivity of

semiconductors45

• n-type semiconductors

– Add more electrons

– Negative charge travels in the

conductance band

Semiconductor Doping

http://3.bp.blogspot.com/-I-mRUp6AXSE/U6ar5CH2C-I/AAAAAAAAAYM/42YTSK8keSU/s1600/10441434_685778644822754_2846024171982000658_n.png

• Doping

– Adding impurity

to a compound

– Changes

conductivity of

semiconductors46

• n-type semiconductors

• p-type semiconductors

– Contains fewer electrons

– “Hole” travels in the valence

band


http://3.bp.blogspot.com/-I-mRUp6AXSE/U6ar5CH2C-I/AAAAAAAAAYM/42YTSK8keSU/s1600/10441434_685778644822754_2846024171982000658_n.png

• Doping

– Adding impurity

to a compound

– Changes

conductivity of

semiconductors47

• n-type semiconductors• Negative charge travels in the

conductance band

• p-type semiconductors– “Hole” travels in the valence

band



The type of element whose

properties are explained by

“band theory” is

a. metals.

b. non-metals.

c. metalloids.

d. diatomic elements.

48

The type of element whose

properties are explained by

“band theory” is

a. metals.

b. non-metals.

c. metalloids.

d. diatomic elements.

49

POLYMERS

50

Polymers

51

• Monomer

• Molecule that

forms the basic

unit for polymers

• Polymers

• Large molecule

• High Molecular weight

• Made from monomers

https://photos.smugmug.com/Graphics/Graphics/i-w9NJQXC/1/L/structure%20of%20monomer%20and%20polymer-L.jpg

Polymers

52

Two primary types of

polymers

• Addition polymers

• Consists of a

repeat unit

equivalent to its

monomer

• Formed when a

bond breaks and

make two new

bonds

• Formed from

double or triple

bond monomershttps://photos.smugmug.com/Graphics/Graphics/i-w9NJQXC/1/L/structure%20of%20monomer%20and%20polymer-L.jpg

https://www.learner.org/courses/chemistry/images/lrg_img/EthyleneMolecule.jpg

• Does not produce by-product

Polymers

53


polymers


• Consists of a

repeat unit

equivalent to its

monomer

• Does not

produce by-

product

• Formed from

double or triple

bond monomers• Formed when a bond breaks

and make two new bonds

http://www.chemistryrules.me.uk/junior/GCSE_polymer_mechanism.gif

Polymers

54


polymers


• Condensation

polymers

• Polymer forms

with elimination of

a molecule

• Monomers used

may be the same

or different

https://photos.smugmug.com/Graphics/Graphics/i-w9NJQXC/1/L/structure%20of%20monomer%20and%20polymer-L.jpg http://s.hswstatic.com/gif/plastic-6.gif

Bulk Properties of Polymers

• Polymers

– Not straight lines

• Longer the chain, the more twisting

– A variety of lengths

– A variety of molecular weights

– May be very flexible (plastics)

– Short range order can lead

to crystallinity


Changing Polymer’s Physical

Properties

• Cross-linking

– Chemical bonding of

polymers to each other

– Causes stiffening

– Strengthens the substance

– Vulcanization

• Cross-linked by short chains

of sulfur atoms

• Used to make rubber stronger


NANOMATERIALS

57

Nanomaterials

• Particles that have

three dimensions

on the 1–100 nm

size


59

100 mm

10 mm

1 mm

100 nm

10 nm

1 nm

0.1 nm

1 mm

1 cm

10 cm

1 m

What size is nano

https://owlspace-ccm.rice.edu/portal/site/CHEM-570-001-Sp07/page/ea15aaa6-a000-41db-00ac-6d32817b0a23

Why Nano

• Different property from bulk

www.chem.rochester.edu 60

Scale bar= 1µm

Size of Silver

Silver Ore

Average Size: Various

Visibility: Eye

Silver Nanoparticles

Average Size: 13nm

Visibility: Electron

Microscope

100nm

http://www.chicagosilver.com/silver.htm61

Silver’s Antimicrobial Properties

Carrot Test

After 3 days After 1 month

Using

Nanosilver

Not

Using

http://www.nanosilver.it/eng/documenti.htm62


Carrot Test

After 3 days After 1 month

Using

Nanosilver

Not

Using

Onion Test

Before Test After Test (day 7)

After Test

(2Month)

http://www.nanosilver.it/eng/documenti.htm63

Why Nano


• Change in property with size and shape

www.chem.rochester.edu 64

Scale bar= 1µm

Physical Property of CdSeQuantum dots are semiconductors this size

65

Variation of color by varying

sizes of nanocrystals© 2015 Pearson Education, Inc.


Growth curves of E.

coli with 107 CFU of

bacteria in the

presence of different

concentrations of

silver nanoparticles:

(□) 0, (●) 10, (▲) 50,

and (■) 100 g cm−3

Growth curve of E. coli,

with 107 CFU/ml, in the

presence of different

concentrations (mg cm-3)

of silver nanoparticles

I. Sondi, B. Salopek-Sondi, Journal of Colloid and Interface Science 275, 177 (Jul, 2004)

Spherical

Nanoparticles

Triangular

NanoparticlesS. Pal, et al., Applied and Environmental Microbiology 73, 1712 (Mar, 2007) 66

Why nano



• High surface to volume ratio

www.chem.rochester.edu

Scale bar= 1µm

67

Surface to Volume Ratio

68

Diameter

(nm)1 3 5 7 10 20 50 100

Surface

to Volume

Ratio3.00 1.00 0.60 0.43 0.30 0.15 0.06 0.03

Volume

(nm3)

V=4/3πr3

4.19 113.10 523.60 1436.76 4188.7 3.4E+04 5.2E+05 4.2E+06

Surface

Area

(nm2)

A =4πr2

12.57 113.10 314.16 615.75 1256.6 5026.553.1E+04 1.3E+05

Why nano



• High surface to volume ratio

• Building blocks for advanced nano-devices

www.chem.rochester.edu

Scale bar= 1µm

69

Silver and technology

• Textile Products – Linens/clothes

– Shoes

– Water purifier filters

• Food storage products – Versatile wrap

– Antibacterial containers

• Paper products– Antibacterial wallpapers

– Antibacterial filters

• Plastic and Electronics – Refrigerator, washer

– Electromagnetic shielding

http://www.nanosilver.it/eng/applicazioni.htm

Computer Appliances

Refrigerator

Microwave Oven

Nano Silver Fruit Juicer

70

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