state of matter
having constituent
particles arranged
in closed manner.
Definiton
particles arrangement
in solid
Properties of definite mass/volume
solids
shape, rigid ,
strong intermolecular
force,
Types of solids:
A.on the basis
of particles
arrangements
crystalline amorphous
solids
solids
1.Definite irregular
shape shape
Crystalline solids
2.long-range short
order
order
3. true
Isotropic
solids
solids
eg.copper, eg. glass Amorphous solids
diamonds
Types of
crystalline
solids
A.molecular
solids
non-polar
consituents
particles
molecules
nature
soft
conductivity
insulator
polar
molecules
soft
insulator
B. Ionic solids
1. consist of IONS
2.columbic/electrostatics forces
3. Insulator
4.Hard and Brittle
5. High Mpt.
eg. CaF2 , ZnS, MgO
hydrogen-bonds
molecules
hard
insulator
c.Metallic solids
D. covalent solids
1. metallic bonding
2. conductor
3. hard and ductile
4. malleable
5.High Mpt.
eg. Fe, Cu, Ag,Mg
1.covalent bonding
2.conductor
3.hard and ductile
4.malleable
5.high Mpt.
eg, SiO2, SiC
Crystal Lattice
A regular ordered arrangements of constituents particle
in three dimensional is Crystal Lattice.
The fixed positions on which the constituents particles
are presents are called lattice points/ lattice sites
.
Unit cells
It is smallest repeating unit in space lattice.
Parameters which characterise a unit cell
seven crystal systems:
Types of unit cells:
effective atom = z
effective
unit cells atoms(z)
S.C
1
B.C.C
2
F.C.C
4
coordination
number
6
8
12
relation
between
a&r
packing
efficiency
a = 2r
53.3%
a = 4r⁄√3
68%
a =2√2r
74%
coordination number:
It is the number of nearest neighbours of a particle
.
Closed Packed Structure
one dimension
two dimension
three dimension
Square close packing
coordination number = 4
type of packing = AAA
Hexagonal close packing
coordination number = 6
types of packing = ABAB
Three dimensional close packing
types of packing = AAAA
Simple cubic lattice
Tetrahedral voids
Type pf pattern = ABABAB
Cordination number = 12
eg. Mn, Zn
octahedral voids
Type pf pattern = ABCABCABC
Cordination number = 12
eg. Cu, Ag
types of voids
a. tetrahedral voids
four spheres are joined to form tetrahedron
b. octahedral voids
six spheres are joined to form tetrahedron
Note:
if number of octahedral voids is n
then, number of tetrahedral voids is 2n
top
side
shape
packing efficiency:
Volume occupied by spheres
P.E =
100%
Total volume of unit cell
Packing efficiency for face centred unit cell = 74%
Packing efficiency for body centred cubic unit cell = 68 %
Packing efficiency for simple cubic unit cell = 52.4%
Density of cell
·Types of defects:
·Point defects
Point defects are the irregularities or deviations from ideal arrangement around a point or an atom in a
crystalline substance.
·Line defects
Line defects are the irregularities or deviations from ideal arrangement in entire rows of lattice points.
·Schottky defect-equal
number of cations and anions are missing.
·Frenkel or dislocation defect
the smaller ion (usually cation) is dislocated from its normal site to an interstitial site
·Classification of solids based on their electrical conductivities
·Types of semiconductors:
·Intrinsic semiconductors
These are those semiconductors in which the forbidden gap is small. Only some electrons may jump to
conduction band and show some conductivity. They have very low electrical conductivity.
Example: Silicon, germanium.
·Extrinsic semiconductors
When an appropriate impurity is added to an intrinsic semiconductor, it is called extrinsic semiconductors.
Their electrical conductivity is high.