1. Chapter 3: Solid State Chemistry
3.6. Concept of types of solids based on bonding
3.7. Concepts of close packing in solids
(Cubic and Hexagonal packing)
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2. Bonding in Solids There are four types of solid:
Molecular (formed from molecules) - usually soft with low melting points and poor conductivity.
Covalent network - very hard with very high melting points and poor conductivity.
Ionic (formed form ions) - hard, brittle, high melting points and poor conductivity.
Metallic (formed from metal atoms) - soft or hard, high melting points, good conductivity, malleable and ductile.
NB: A solid with only one type of atom is also called ‘atomic’
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3. CLASSIFICATION OF SOLIDS BASED ON BONDING
CRYSTALS
Molecular
Non-molecular
COVALENT
Molecule held together by primary covalent bonds
Intermolecular bonding is Van der walls
IONIC
METALLIC
CLASSIFICATION OF SOLIDS BASED ON BONDING
COVALENT
IONIC
METALLIC

4. Bonding in Solids
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5. Three Types of Crystalline Solids
atomic solid
ionic solid
molecular solid

6. Bonding in Solids Covalent Network Solids
Intermolecular forces: dipole-dipole, London dispersion and H-bonds.
Atoms held together in large networks.
Examples: diamond, graphite, quartz (SiO2), silicon carbide (SiC), and boron nitride (BN).
In diamond:
each C atom has a coordination number of 4;
each C atom is tetrahedral;
there is a three-dimensional array of atoms.
Diamond is hard, and has a high melting point (3550 C).
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7. Bonding in Solids Covalent Network Solids
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8. Covalent Crystals Lattice points occupied by atoms
Held together by covalent
Hard, high melting point
Poor conductor of heat and electricity
carbon
atoms
diamond
graphite

9. What hybrid state do you think the carbon has?
Diamond
Hard Structure
- Tetrahedral atomic arrangement
What hybrid state do you think the carbon has?
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10. Bonding in Solids Covalent Network Solids In graphite
each C atom is arranged in a planar hexagonal ring;
layers of interconnected rings are placed on top of each other;
the distance between C atoms is close to benzene (1.42 Å vs Å in benzene);
the distance between layers is large (3.41 Å);
electrons move in delocalized orbitals (good conductor).
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12. What hybrid state do you think the carbon has?
Graphite
- Form planar sheets actually more stable than diamond
What hybrid state do you think the carbon has?
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13. Fullerene-C60 Closely Related to Graphite Structure
Both Six-membered and Five-membered Rings of Carbon are Found in the Fullerenes
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14. Artists carbon nanotubes, multiwalled MWCNT
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15. Forming Carbon Nanotubes
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16. Real carbon nanotubes
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17. IONIC BONDING

18. Bonding in Solids Ionic Solids NaCl Structure CsCl Structure
Each ion has a coordination number of 6.
Face-centered cubic lattice.
Cation to anion ratio is 1:1.
Examples: LiF, KCl, AgCl and CaO.
CsCl Structure
Cs+ has a coordination number of 8.
Different from the NaCl structure (Cs+ is larger than Na+).
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19. The CsCl and NaCl Structures
CsCl NaCl
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20. Cubic and Hexagonal Unit Cells
There are 7 basic crystal systems, but we are only concerned with
CUBIC and HEXAGONAL.
All sides
equal length
All angles
are 90 degrees
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24. Cubic Unit Cells of Metals
Simple cubic (SC)
Body-centered cubic (BCC)
Face-centered cubic (FCC)
1 atom/unit cell
2 atoms/unit cell
4 atoms/unit cell
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25. Number of Atoms per Unit Cell
Unit Cell Type Number Atoms SC
BCC
FCC 1 2 4
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33. The Sodium Chloride Lattice
Many common salts have FCC arrangements of anions with cations in OCTAHEDRAL HOLES — e.g., salts such as CA = NaCl
• FCC lattice of anions ----> 4 A-/unit cell
• C+ in octahedral holes ---> 1 C+ at center
+ [12 edges • 1/4 C+ per edge]
= 4 C+ per unit cell
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34. Your eyes “see” 14 Cl- ions and 13 Na+ ions in the figure
Ion Count for the Unit Cell: 4 Na+ and 4 Cl- Na4Cl4 = NaCl
Can you see how this formula comes from the unit cell?
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35. NaCl Construction Na+ in octahedral holes
FCC lattice of Cl- with Na+ in holes
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37. Simple Ionic Compounds
CsCl has a SC lattice of Cs+ ions with Cl- in the center.
1 unit cell has 1 Cl- ion plus
(8 corners)(1/8 Cs+ per corner)
= 1 net Cs+ ion.
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