Transcript Chapter 13 The Chemistry of Solids Types of Solids • Metals • Network • Ionic • Molecular • Amorphous.

Chapter 13
The Chemistry of Solids
Types of Solids
• Metals
• Network
• Ionic
• Molecular
• Amorphous
Chapter 13
The Chemistry of Solids
Types of Solids
•
•
•
•
•
Metals
Network
Ionic
Molecular
Amorphous
Examples
Copper
Quartz
NaCl
CO2, CI4
glass, polyethylene
Types of Solids
• Metals
• Network
• Molecular
Characteristics
Copper - malleable
Quartz – non-malleable
sulfur (S8)
•CO2, CI4 – low melting pt
• Ionic &
muscovite– cleaves easy
Network,
Layered structure
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
UNIT CELL is the smallest piece of the
pattern that generates the lattice.
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.
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
One result of a metal’s “choice” to adopt a
cubic, bcc or fcc lattice are metal properties
Simple Cubic
Body Centered Cubic
Face Centered Cubic
Packing a Square Lattice:
Makes a simple cubic cell
Can you pack spheres more densely?
The Rhomb is the
Unit Cell Shape
of
Hexagonal Lattices
Closest Packing:
hexagonal layers build up 3D solid
Find the triangular gaps in the Pink layer
Note how layers “sit” on top of each other:
The Cyan layer
covers the “up”
triangles of the
Pink layer
The Yellow layer
covers the “down”
triangles of the
Pink layer
This packing sequence is A B C A B C,
Where B and C cover different “holes” in A
A
B
C
A
B
C
A
B
Packing direction
C
A
Packing direction
B
A
C
B
A
C
B
A
C
ccp
Cubic
Closest
Packing:
ABCABC…
C
B
A
C
B
A
CCP viewed as packing layers
CCP viewed unit cell;
LOOK! It’s face centered cubic!!!
CCP = FCC!!
….mmmMMM
Smaller atom like C in iron
Effect of added
atoms and
grains
on
metal structure.
Larger atom
like P
in iron
Defects and grain boundaries “pin” structure.
All these inhibit sliding planes and harden the metal.
Second crystal
phases
precipitated
Defects
in
metal
structure
From Metals to Ionic Solids
Will ionic solids pack exactly like metallic solids?
From Metals to Ionic Solids
Build up Ionic Solids conceptually like this:
• assume Anions are larger than Cations, r- > r+
• pack the Anions into a cubic lattice: ccp, simple or bcc
• add Cations to the interstitial spaces (“Mind the gap!”)
r- + r+
2 x r-
2 x r-
How to
draw this
The Simplest Ionic Solid is CsCl, simple cubic
Start with
simple cubic
Unit cell of Cl- ion
Then add one
Cs+ in center
Z=
C. N. (Cs) =
How to make NaCl: start with fcc unit cell of Cl- ions
Add Na+ in between
Add Na+ in between, everywhere
Z=
C. N. (Na) =