Here are the definitions and differences you asked for: Short range order - Atoms are arranged in a disordered manner within a small region but this arrangement does not extend over long distances. Anisotropic - A material whose physical properties vary with the direction of measurement. Unit cell - The smallest repeating unit that constructs the entire crystal by translation. Voids - Empty spaces between closely packed spheres in crystal structures. There are two types - octahedral and tetrahedral voids. Impurity defect - Occurs when an atom of one element replaces an atom of the host element in its normal lattice position. Monoclinic - Unit cell with two axes at 90 degrees and one axis not at 90 degrees

1. THE SOLID STATE
Subject : chemistry
Class: XII

2. Name : Sulekha Rani.R.
Designation: P.G.T. Chemistry
School: Kendriya Vidyalaya INS
Dronacharya
Emailid: sulekharanir@gmail.com

3. Objectives of the lesson
plan
The pupil acquires knowledge about
the concept of type of solids,type
of unitcells, packing in
crystals,packing efficiency,defects
in crystals.
The pupil develops understanding
about the above mentioned concept
.
The pupil applies the above concept
in unfamiliar conditions.

4. CONTENTS
Classification of solids
Crystalline solid & Amorphous solids
Long range and short range order
Isotropy and anisotropy
Characteristic feature of crystals
Unit cell and crystal lattice
Characteristic parameters of a unit cell
Types of unit cell
Packing in crystals
1D, 2D and 3D packing of spheres
Td and Oh voids
Packing efficiency
Packing efficiency of simple cubic, bcc and hcp.

5. The solid state
•WHY STUDY SOLIDS ?
Variety of properties
Most used in day to day life
These properties stem from within !!!

6. The origin of the word “Crystal”
Krystallos – Greek name for Quartz
Romans used
quartz crystals
to cool
themselves on
HOT days
The Greeks
used quartz
crystals to
sterilize battle
wounds
The ancient Greeks believed that
drinking from an Amethyst Goblet
does NOT make you drunk !!!
Amethyst-a purple quartz- was
worn by the bishops – and signifies
devotion

7. Diamond Salt
Metal Sugar
Amorphous
ionic
conductors
Glass
Wax
Metallic Glass
Classification A
1.Crystalline 2. Amorphous
CLASSIFICATION OF SOLIDS

8. i) Covalent
ii) Ionic
iii)Metallic
iv)Molecular
a) van der Vaals
b) Dipole
c) H-bonding
i) Covalent
ii) Ionic
iii)Metallic
iv)Molecular
a) van der Vaals
b) Dipole
c) H-bonding
1.Crystalline 2. Amorphous
Type of bonding
Classification B

9. Crystalline solids
Definition of crystalline solids
Definition of long – range
order
Definition of anisotropic

10. Definition
The solids in which atoms or molecules
are arranged in a very regular and
orderly fashion in a three dimensional
pattern.
Examples
sodium chloride, sulphur and sugar.
Crystalline solids …

11. A crystal is made up of either atoms,
molecules or ions; they are known as
ultimate particles.
The X-ray studies reveal that the
particles are arranged in a definite
pattern throughout the entire three –
dimensional network of a crystal.
This definite and ordered arrangement of
molecules, atoms or ions extends over a large
distance.
This is termed as long – range order.
Crystalline solids – Long-range order

12. An ordered stack A disordered heap
The consequence of long range order

13. Crystalline solids exhibit different physical
properties in all directions. This property is
called anisotropic.
It can be defined as a difference in a physical
property (absorbance, refractive index, density,
etc.) for some material when measured along
different axes.
For example, the electrical and thermal conductivities
are different in different directions.
Crystalline solids – anisotropic

14. Crystalline solids – anisotropic (contd.)
This is the arrangement of Na+
ions (red balls) and Cl- ions (blue
balls) in NaCl crystal.
Consider the x-axis; alternate
arrangement of red and blue balls
Consider the y-axis; again
alternate arrangement of red and
blue balls.
Consider z-axis; arrangement of
only red balls or only balls.
This shows that the physical properties measured in different
directions will be different. Thus the crystalline solids are
anisotropic.
x
z
A model 3-D crystal

15. Properties of Crystalline solids
 Crystalline solids are Incompressible
They have definite pattern of arrangement
of ions, molecules or atoms in three
dimensional network.
They have rigid structure
They have characteristic geometrical forms
Crystalline solids have sharp melting point
They have anisotropic property

16. Amorphous solids
In Greek Amorphous means
“without form”
Definition of Amorphous solids
The solids in which the atoms or molecules
are not arranged in a very regular and orderly
fashion in a three dimensional pattern
Examples
glass, rubber and plastics

17. Isotropic – It is a
characteristic of amorphous
solids since they exhibit
same physical properties in
all directions.
Isotropy means homogeneity
in all directions
The word is made up from
Greek iso (equal) and
tropos (direction).
Amorphous solid are isotropic
This is a polycrystalline
Material. Consider any axis
– x, y, or z axis; the physical
property that is measured
will be the same all the
directions .

18. Amorphous solids are super
cooled liquids ???
Ancient glasses turn milky !!
Window panes get thicker at the bottom !!
Fused silica divitrifies !!

19. i) Glass transition
ii) Isotropic physical
properties
iii)Short ranger order
iv)No Characteristic
heats of fusion
v) Irregular cleavage
i) Sharp melting point
ii) Anisotropic
physical properties
iii)Long range order
iv)Definite heats of
fusion
v) Cleavage
Properties of solids
1. Crystalline. 2.Amorphous
Difference between crystalline & amorphous solids

20. Size and shape of crystals
Size of the crystals depends on rate at which it is
formed: the slower the rate, the bigger the crystal
size.
Small copper suphate crystals Bigger copper suphate crystals

21. Characteristic feature of crystals
1. Faces: Crystals are bound by plane faces
Classification: (i) like faces – A crystal having all
faces alike e.g. Fluorspar, (ii) Unlike faces - A crystal
having all faces not alike e.g. Galena
2. Form: All the faces corresponding to a crystal are
said to constitute a form.
3. Edges: The intersection of two adjacent faces gives
rise to the formation of edge.
4. Interfacial angle: The angle between the normals to
the two intersecting faces.

22. Unit cell
Definition
The smallest structure of which the crystalline solid is
built by its repetition in three dimensions is called a unit
cell.

23. UNIT CELL REPRESENTATION
unit cell
1
5
2
3 4
6
7 8

24. The repeating unit of the lattice is called the
unit cell ANIMATION

25. Characteristic parameters of a unit cell
1. Crystallographic axes
The lines drawn parallel to the
lines of intersection of any three
faces of the unit cell which do not
lie in the same plane.(OX, OY,
OZ)
2. Interfacial angles
The angles between the three
crystallographic axes. (, , )
3. Primitives
The three sides of a unit cell
(a, b, c).
A unit cell

26. The Lattice parameter (s)
, ,  and a, b, c

27. Types of unit cells
1) Cubic
2) Triclinic
3) Monoclinic
4) Orthorhombic
5) Tetragonal
6) Hexagonal
7) Rhombohedral
There are seven classes of unit cells.
They are

28. The Seven primitive unit cells

29. Types of unit cells (Contd.)
Simple cubic
One atom occupies each of
the eight corners of the cube.
The distance from atom to
atom along lattice is the same
in every direction, and the
angle between each axes is
90o
.
Simple cubic structure

30. Simple cube

31. Body-centered cubic
In body-centered cubic
system, one atom occupies
each of the eight corners of
the cube and there is an
additional atom in the
center of the cube.
Types of unit cells (Contd.)
Body - centered cubic
structure

32. . Body centered Cube

33. Face-centered cubic
In faced-centered cubic structure.
One atom occupies each of the
eight corners of the cube and there
is an atom at the center of each of
the six faces of the cubic unit cell.
This crystal pacing form
has higher density than the
body-centered cubic structure.
Types of unit cells (Contd.)
Body - centered cubic
structure

34. Face cenetred cube

35. Cubic Unit Cells

36. Lattice positions
Atoms or ions are shared between adjacent unit
cells.
The lattice position of the atom or ion determines
the no of unit cells involved in the share.
Body : Not shared
Face : shared by two unit cells
Edge : shared by four unit cells
Corner : shared by eight unit cells

37. ANIMATION TO EXPLAIN CONTRIBUTION
AND FORMATION OF CRYSTAL LATTICE

38. hcp crystal formation

39. Packing of spheres
1 . Close packing of spheres in one dimension

40. 2D packing of spheres
primitive packing
Square close packing
(low space filling)
close packing
hexagonal close packing
(high space filling)
scp hcp

41. ANIMATION TO SHOW 2D ARRANGEMENT
OF SQUARE CLOSE PACKING (scp )

42. ANIMATION TO SHOW 2D ARRANGEMENT OF
HEXAGONAL CLOSE PACKING (hcp )

43. 3D PACKING OF SPHERES IN CRISTALS
1. TYPES OF VOIDS
2. CUBIC CLOSE PACKING (AAA…)
3. SQUARE CLOSE PACKING (ABCABC…)
4. HEXAGONAL CLOSE PACKING (ABAB ...)

44. 3D packing of spheres
Animation
SIMPLE CUBIC

45. 3D packing of spheres
Animation
BODY CENTERED CUBIC

46. 3D packing of spheres
Animation
FACE CENTERED CUBIC

47. 3D packing of spheres –
simple unit cell
3D close packing
from 2D square
close – packed
layers form simple
cubic lattice
• The second layer is placed
exactly same as the firs layer,
so that the spheres of both
the layers are perfectly
aligned.
• This type of arrangement is
known as AAA….. Type
arrangement
• The unit cell generated is a
simple unit cell.

48. Tetrahedral and
Octahedral holes
Tetrahedral hole
Td
Octahedral hole
Oh
Tetrahedral hole
Octahedral hole

49. Octahedral void Tetrahedral void
TYPES OF VOIDS

50. Locating tetrahedral void

51. Locating OCTAHEDRAL VOID
- at the edge

52. Locating OCTAHEDRAL VOID
- at the centre

53. 3D packing of spheres hcp or ccp
arrangement
Covering of
tetrahedral voids
results in hcp
arrangement
Covering of
octahedral voids
results in ccp
arrangement

54. Close Packing in Three Dimensions
Two layers,
stacked, give two
different locations
for the third layer
Third layer directly
above first layer: HCP
Third layer over the octahedral
holes in the second layer: CCP

55. ANIMATION FOR 3D PACKING IN hcp

56. ANIMATION FOR SCP

57. Packing efficiency in hcp and ccp
structures
2 2 2 2
2 2 2
3 3
In C
AC = b = BC + AB
= 2 or = 2
If is the radius of the sphere, we find
= 4 = 2 or
4
= 2 2
2
Volume of the cube = (2 2 )
In each unit cell in structure has
a a a b a
r
b r a
r
a r
a r
ccp
 
 

3
effectively 4 spheres
4
The total volume of the sphere = 4
3
volume occupied by four spheres in the unit cell 100
Packing efficiency = %
Total volume of the unit cell
=
r 

3
3
4
4 100
3
% = 74%
(2 2 )
r
r
 
   
 

58. Packing efficiency in bcc structures
2 2 2 2
2 2 2 2 2 2
In EFD
b = 2 or
b = 2
In FD
c = a b 2 + = 3
The length of the body diagonal = 4 As all the three spheres
along the diagonal touch each other
3 = 4
4
= and
3
a a a
a
a a a
c r
a r
a r

 
 
 

3
3
3
4
=
3
3
r =
4
4
In bcc, 2 atoms normally present in the unit cell and their volume is 2
3
volume occupied by two spheres in the unit cell 100
Packing efficiency =
Total volume
a r
a
r
 
 
 
 
 
 
 

3
3
%
of the unit cell
4
2 100
3
= % = 68%
4
3
r
r
 
 
 
 
 
 
  

59. Packing efficiency in simple cubic
lattice
 
33 3
3
The volume of the cubic unit cell = a = 2r = 8r
= 2
The simple cubic lattice contains only one atom
4
The volume occupied by one atom =
3
volume occupied by one atom
Packing efficiency =
a r
r
 
 
 

3
3
100
%
Total volume of the unit cell
4
100
3
= % = 52.4%
8r
r
 
 
 

 

60. DEFECTS IN SOLIDS
1.POINT DEFECT
1. STOICHIOMETRIC DEFECT
2. IMPURITY DEFECT
2. NON -STOICHIOMETRIC DEFECT
SCHOTTKY DEFECT
FRENKEL DEFECT
METAL EXCESS DEFECT
METAL DEFICIENCY DEFE
due to anion vacancies
Due to
extra cation

61. POINT DEFECT
Definition
The irregularitiesor deviations from ideal
arrangementaround point or an atom in a
crystallinesubstances

62. STOICHIOMETRIC DEFECT
Defects that did not disturb the
stoichiometry of the solids
In nonionicsolids:
(i) vacancy defect
(ii) interstitial defect
In ionicsolids:
(i) schottky defect
(ii) Frenkel defect

63. POINT DEFECT  STOICHIOMETRIC
DEFECT VACANCY DEFECT
This defect arises when some lattice
sites are vacant

64. POINT DEFECT 
STOICHIOMETRIC DEFECT
INTERSTITIAL DEFECT
This defect arises when some constituent
particles occupy an interstitial site

65. Defects in ionic solids
In ionic solids they will maintain the
neutrality
Schottky defect:
T his defect arises due to equal number of
anions and cations are missing from the
lattice position.
Frenkel defects:
Cation is dislocated from its normal site to
an interstitial site

66. Schottky defect
Example : NaCl, KCl . AgBr

67. POINT DEFECT  STOICHIOMETRIC DEFECT VACANCY DEFECT
FRENKEL DEFECT
EXAMPLE : ZnS ,AgBr
CATION
ANION

68. IMPURITY DEFECT
EXAMPLE : NaCl IS DOPPED BY CdCl2
Cl--
Na+
Cd2+

69. IMPURITY DEFECT
EXAMPLE : NaCl DOPPED BY AlCl3
Al 3+
Na+
Cl--
FIRST PPT

70. Query session
What do you meant by the following terms
short range order, anisotropic, unit cell, voids, impurity
defect
Differentiate the following.
monoclinic & triclinic
octahedral voids &tetrahedral voids
b.c.c and f.c.c
scottkey defect and frenkal defect
isotropic and anisotropic
hexgonal and square close packing.
Give reason
Due to scottkey defect no change in density
ZnS showing Frenkel defect

71. REFERENCES :
N.C.E.R.T. Text book of chemistry class XII
Physical chemistry text book by Puri and sharma
Solid state by A.K. Day
www.google.com
http://www.chm.davidson.edu/chemistryapplets/Crystal
s/ClosestPackedStructures.html
http://www.chemistry.nmsu.edu/studntres/chem116/not
es/crystals.htm

72. THANK YOU
SULEKHA RANI.R
P.G.T.CHEMISTRY
KENDRIYA VIDYALAYA
INS DRONACHARYA