Transcript Lecture 13.1 - Bryn Mawr College

Chapter 13
The Chemistry of Solids
Chapter 13
The Chemistry of Solids
Types of Solids
• Metals
• Network
• Ionic
• Molecular
• Amorphous
Chapter 13
The Chemistry of Solids
Types of Solids
•
•
•
•
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Examples
Metals
Copper
Network
Quartz
Ionic
NaCl
Molecular
CO2, CI4
Amorphous
glass, polyethylene
Chapter 13
The Chemistry of Solids
Types of Solids
• Metals
• Network
• Molecular
Characteristics
Copper - malleable
Quartz – non-malleable
CO2, CI4 – low melting pt
• Ionic &
muscovite– cleaves easy
Network,
Layered structure
Table 13.1 Study this!
The Chemistry of Solids
What characteristic do these solids share?
The Chemistry of Solids
What characteristic do these solids share?
Repeating Structural Pattern
other terms:
Lattice
Array
Crystal Structure or
Crystal Lattice
The Chemistry of Solids
What repeats? Simplest Repeating Pattern:
UNIT CELL is the smallest piece of the
pattern that generates the lattice.
• in 2 D — wallpaper or Escher
• in 3 D — crystal structures
The Chemistry of Solids
UNIT CELL is a conventional choice.
May have several unit cells possible,
Different in shape and/or size.
Translation directions
The Chemistry of Solids
UNIT CELL is a conventional choice.
May have several unit cells possible,
Different in shape and/or size.
Is this a good unit cell?
YES! This Unit Cell generates
entire pattern by translation ONLY
Is this 2nd cell a good unit cell?
Is this 2nd cell a good unit cell?
Yes! It also generates the pattern
by translation.
1st cell is smaller: contains 1 white fish
2nd cell is larger: contains 2 white fishes
1st & 3rd cell primitive: contains 1 white fish
2nd cell is centered: contains 2 white fishes
m
m
m
m
One C4 and 2 types of mirrors = 4m
Asymmetric Unit
= smallest piece
that generates
entire unit cell
Triclinic cells
Monoclinic cells
(lowest symmetry)
Orthorhombic
Cells
Tetragonal Cells
Cubic Unit Cells
(highest symmetry)
Hexagonal Cells
Cubic Unit Cells have
a= b=c
a = b = c = 90 deg
b
c
a
Three Types of Cubic Unit Cells
b
c
a
Simple Cubic
Body
Centered
Cubic
Face
Centered
Cubic
These Three Cubic Unit Cells are Structures
of most Metallic Elements
(also hexagonal, hcp, to be seen Friday)
Cu, Ag, Au are all fcc
Cr, Mo, W are all bcc
Only Po is simple cubic (rare— why?)
Simple Cubic
Body
Centered
Cubic
Face
Centered
Cubic
What is one result of a metal’s “choice”
to adopt a cubic, bcc or fcc lattice?
Simple Cubic
Body Centered Cubic
Face Centered Cubic
Primitive cell
Asymmetric unit = smallest portion needed to create unit cell
2 Asym./cells