solid state and surface chemistry (lecture 1)

S ^OLID S ^{TATE AND} S ^URFACE C ^HEMISTRY

( ^LECTURE 1)

Dr. Saedah Rwede Al-Mhyawi Assistant professor

Contact Info: Salmhyawii@kau.edu.sa Web Site: http://Salmhyawi.kau.edu.sa Office hoursT,R 10-11,12-1 , W 11-1

Thanks Dr.Laila Al-harbe

C

HEM

. 345

 Objectives of the course :

 The course aims to give the students the principles in solid state, surface chemistry, colloids and Catalysis.

 Course Description :

 Crystal system- unit cell- X-ray diffraction- cubic crystals- Types of semiconductors- Adsorption of gases- Surface Area-Adsorption

from solutions- Homogeneous and heterogeneous Catalysis- Enzyme Catalysis- Colloids; their types , methods of preparations and

properties.

 Main text book:

 Physical Chemistry, J. de Paula & P. Atkins, 7th ed., 2001, W. H.

Freeman.

 Subsidiary books:

 Introduction to Surface Chemistry and Catalysis, G. A. Somorjai, 1994,Wiley-Interscience.

 Physical Chemistry, W. Moore and Lands.

 Chemistry, by Chang, 10^th. ed., 2007, McGraw-Hill.

G

^RADING

 ASSIGMENTS = 5 MARKS

 PRESENTATION = 15 MARKS

 QUIZ (I) = 20 MARKS

 QUIZ (I) = 20 MARKS

 FINAL = 40 MARKS

 TOTAL = 1000 MARKS

 PRESENTATION TOPICS

 NANOSUMICONDUCT ORS

 NANOSOLIDS

B

^{RIEF HISTORY AND NOTABLE} CONTRIBUTIONS FROM SOLID STATE CHEMISTRY

 August Bravais (1848): more math

 - mathematically proved that there are 14 distinct ways to arrange points in space

 X-ray crystallography in the early 1900’s by William L Bragg

 Zeolite and platinum-based catalysts for petroleum processing in the 1950’s

 High-purity silicon, a core component of microelectronic devices in the 1960’s

 Microwave dielectrics (wireless communications) in the 1970’s

 “High temperature” superconductivity in the 1980’s

 Giant and colossal magnetoresistive (CMR) materials in the 1990’s

 Nano-, energy storage and generation, and functional materials in the 2000’s

I

NTRODUCTION TO SOLID STATE

 The solid state includes most of the materials that make modern technology possible.

 a) It includes the wide varieties of steel that are used in architecture and engineering.

 b) The semiconductors and metallic conductors that are used in information technology and

power distribution.

 c) The ceramics that increasingly are replacing metals.

 d) The synthetic and natural polymers that are used in the textile industry and in the fabrication of many of the common objects of the modern

world.

A

^IM

 To obtain an understanding of the concepts used to describe crystal structure as well as knowledge of the lattice types.

 The physical properties of solids (including rigidity, brittleness, and electrical

conductivity) depend on their structure, i.e.

their arrangement of atoms.

 Therefore it is necessary to understand the

various crystal structures before proceeding to physical properties

O

^BJECTIVES

By the end of this section you should:

 be able to identify a solid state

 Identify differences between crystalline and amorphous solids.

 Explain how the arrangement of atoms and

molecules in solids determines their properties.

Its butter to review section 11-2 (Chemistry, by Chang, 10^th. ed., 2007, McGraw-Hill).

The three states of matter.

T

^{HE SOLID STATE}

 In a solid, the attractive forces are much stronger than the kinetic energy of the particles, so the atoms, molecules, or ions are held in a specific arrangement and can only wiggle around in place.

 Molecules are held rigidly (no free motion)

 Atoms incompressible

 Usually more dense than H₂O

 A crystal is solid in which the constituent atoms , molecules , or ions are packed in regularly ordered, repeating pattern extending in all three spatial

dimensions

 Crystals are solid - but solids are not necessarily crystalline

T

WO GENERAL TYPES OF SOLIDS

 crystalline - rigid, ordered arrangement of atoms,

ions, or molecules

 amorphous - random disordered arrangements of atoms, ions, or

molecules

A

^MORPHOUS

S

^OLIDS

 solids that lack a regular 3D arrangement of atoms

 generally formed by rapid cooling, example: glass

 an optically transparent fusion product of inorganic materials

 that has cooled to a rigid state without crystallizing

 800 kinds

 usually SiO2 and things like Na₂O, B₂O₃, or MO_x for color

 The color of glass is due to largely to the presence of metal ions

 (e.g., CuO gives blues – UO₂ gives yellows – Fe₂O₃

gives greens – small particle of Gold gives red color ))

A glass is an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing

Crystalline

quartz (SiO₂) Non-crystalline quartz glass

1. chemically inert

2. electrically insulating 3. mechanically brittle 4. optically transparent 5. visually arresting

Properties of Oxide Glasses

TYPES OF CRYSTALLINE SOLIDS

 Classification is based on the nature of intermolecular forces.

 The stronger the intermolecular forces, the higher melting the material(if the structure is ordered).

 Intermolecular forces control whether the material is hard or soft, flexible or stiff, brittle or tough,

conducting or insulating.

 types of crystalline solids

 1- ionic Crystals

 2- Molecular Crystals

 3- Network Crystals

 4- Metallic Crystals

 5- Polymeric Solids

Classifying Solids

1-

^IONIC

C

^RYSTALS

 Building blocks are anions and cations

 Crystalline solids

 Solid is kept together by Coulombic forces. The forces are not localized as is the case in covalent bonds.

 These forces are much stronger than the intermolecular forces in molecular crystals.

 ions pack themselves so as to maximize the attractions and minimize repulsions between the ions.

 have a high melting point, are hard and brittle

 Poor conductor of heat and electricity ( conduct electricity as molten and solution)

 – Solubility depends on ionic character of the chemical bonds,

 – Examples of ionic solids: NaCl, ZnS , salts.

NaCl does not exist as

a single unit like a molecule.

2- M

^OLECULAR

C

^RYSTALS

 Building block is the molecule

 Crystalline or amorphous

 Solid is kept together by intermolecular forces (dispersive, dipolar or hydrogen bonding).

 These forces are weak compared to covalent or ionic forces.

 Low melting point and weak mechanical and electrical properties (soft).

 Melting is a simple break-up of intermolecular forces with preservation of molecular structure (no degradation because low temperature).

 Solubility of molecular solids. LIKES DISSOLVE LIKES

 Aqueous solutions of molecular solids do not conduct electricity any better than water itself.

 Examples of molecular solids: dry ice, wax, aspirin, sugar, most drugs

3- C

^OVALENT

(N

ETWORK

) C

^RYSTALS

 Only one building block: a giant molecule in which all atoms are covalently bonded to their neighbor:

 Covalent bonding occurs in many directions in covalent solids Mechanical properties are outstanding along covalent bonding direction (Hard, high melting point)

 Bonding can lead to 3D, 2D or 1D giant molecules.

 Poor conductor of heat and electricity

 – Examples: Diamond (3D), Graphite Asbestos (silica) (1D etc…

Graphite ^Diamond

4- M

^ETALLIC

C

^RYSTALS

 Building blocks are cations of metal atoms and electrons:

 The metallic bonding is then again based on columbic interactions between cations and electrons.

 The fact that the electrons are almost free and the cations are arranged on a lattice (crystal order) is at the origin of the excellent thermal and electrical conductivities as well as

optical properties of metals.

 The strength of metallic bonds can vary widely (Hg vs W)

 Further variability in the properties is obtained by making alloys (mixtures of metal with either another metal (pewter, solder) and some other substance( iron with carbon to make steel)

 Metals, obviously, have widespread applications as

engineering materials. Strength (can sustain high stress) but no brittleness (can deform significantly).

 Disadvantage in many applications cost and density. Cost:

Processing at high T required for both the raw material and the pure meta

Cross Section of a Metallic Crystal nucleus &

inner shell e^- mobile “sea”

of e^-

• Soft to hard, low to high melting point

• Good conductors of heat and electricity

Crystal Structures of Metals

P

OLYMERIC

S

OLIDS

 Only one building block and two types of bonds:

covalent bonds within the polymer chain and weak intermolecular bonds between chains.

 Think of polyethylene as intermediate between methane and diamond… but more complicated.

 Crystalline polymers are not truly crystalline.

They are semi-cristalline, in the sense that

chains are so long (ca. micrometer), that they can participate in crystalline and amorphous regions

Types of Crystals

In terms of the periodic table, is there an abrupt or gradual change between ionic and covalent bonds?

A. An abrupt change that occurs across the metalloids.

B. Actually, any element of the periodic table can form a covalent bond.

C. There is a gradual change: the farther apart, the more ionic.

D. Whether an element forms one or the other

depends on nuclear charge and not the relative positions in the periodic table.

Atoms of metallic elements can form ionic bonds, but they are not very good at forming covalent bonds. Why?

A. These atoms are too large to be able to come in close contact with other atoms.

B. They have a great tendency to lose electrons.

C. They are on the wrong side of the periodic table.

D. Their valence shells are already filled with electrons.