Structures and Types of
Solids
Two types of solids
1.
Crystalline solids
 highly
regular
arrangement of their
particles
 crystals- at microscopic
level
How are they crystals?
Lattice
- 3-D system of
points indicating
position of ions, atoms
or molecules that make
up the substance
Unit cell
Smallest
repeating
pattern of the latticeextend in all directions
for the structure
3 types of unit cells
 A.
Simple cubic

polonium metal
 B. Body centered cubic

Uranium metal
 C. Face centered cubic

Gold metal
Two types of solids
2.
Amorphous solidsconsiderable disorder
in their structure
EX- glass- liquid that is
“frozen in place”
Crystalline solids??
How
do we determine
the structure of the
solid?
X-ray diffraction!!
Bragg equation
 1915
Noble prize in physics
 n = 2dsin
 where n= integer
= wavelength of x-rays
d= distance b/w atoms
= angle of incidence
Types of crystalline
solids
Easy
to classify based
on what particle is at
lattice point
Types of crystalline
solids
 Explains
why solids have
different properties
 melting point
 conductivity
 ductility
Three types
1.
Ionic solids- have
ions at the points of the
lattice
NaCl
Three types
2.
Molecular solid- have
discrete covalently
bonded molecules at
lattice points
 ice
Three types
3.
Atomic solidssubstances that have
atoms at the lattice
points
 C, B, Si and all metals
Three types of atomic
solids
A.
metallic solidsdelocalized
nondirectional covalent
bonding
Three types of atomic
solids
B.
network solidsatoms bond with strong
directional covalent
bonds that lead to giant
molecules (networks)
Three types of atomic
solids
C.
Group 8 solidsnoble gas elements are
attracted by London
dispersion forces
Structure and Bonding
in Metals
Metals-
high thermal
and electric conductivity,
malleability, ductilitydue to nondirectional
covalent bonding
Closest packing
Spherical
atoms packed
together and bonded in
all directions
spheres packed in
layers-each surrounded
by 6 others
Three arrangements
 Hexagonal
closest
packed structure (hcp)aba arrangement
 has hexagonal unit cell
hcp structure
Every
other layer has
the same vertical
position
EX: Mg, Zn
Three arrangements 
Cubic
closest packed
structure (ccp)- abc
arrangement
face-centered cubic cell
ccp structure
Every
4th level
occupies the same
vertical position
EX: Al, Fe, Cu, Co, Ni
Three arrangements
Body
centered cubic
unit cell (bcc)spheres touch along
the body diagonal of
the cube
bcc unit cell
Most
spread apart
arrangement
EX: alkali metals
Counting atoms...
Need
to know number
of atoms in a unit cell
Face-centered
8
cubes share one cell
1/8 x 8 corners +
1/2 x 6 faces =
net 4 whole spheres
Density of ccp solid
Ag
crystallizes in a ccp
structure. The radius of
a silver atom is 144pm.
Calculate the density of
solid silver.
Bonding models for
metals
Model
must account for
physical properties:
A. shape can be
changed fairly easilymalleable and ductile
Bonding models for
metals
B.
durable
C. high melting points
Bonding models for
metals
Indicates
the bonding is
STRONG and
NONDIRECTIONAL
or difficult to separate
metals atoms, but easy to
move them
The model is...
Electron
“sea”model
metal cations in sea of e
(mobile e for conductivity
and cations can be
moved around when
hammered
Last topic-metal alloys!
Metals
introduced into
the crystal structure of
other metals
Alloy
A
substance that
contains a mixture of
elements and has
metallic properties
Two types of alloys
Substitutional
alloysome of the host metal
atoms are replaced by
other metal atoms of
similar size
Substitutional alloys
EX:
Brass (1/3 of
copper atoms replaced
with zinc)
Pewter (85%Sn, 7%Cu,
6%Bi, 2%At)
Two types of alloys
Interstitial
alloyformed when some of
the holes in a close
packed metal structure
are occupied by smaller
atoms
Interstitial alloy
EX:
Steel (carbon
atoms into iron)
Strengthens iron by
adding strong
directional bonds