THE SOLID STATE -nli-PPT.pptx IMPORTANT FOR STUDENTS

PART -1 OUTLINE
Characteristics of solids
Classification of solids
Classification of crystalline solids

Characteristics of Solids
 Solids have definite shape
and volume, rigidity
incompressibility and high
density .
 In solids the constituent
particles are very closely
packed and occupy fixed
positions.
Constituent particles
oscillate about their mean
position

CLASSIFICATION OF SOLIDS
Types:-
1.Crystalline solid. 2.Amorphous solid.
Amorphous(Glass)
800px-Quartz,_Tibet from
wikipedia.jpg ,
Crystalline(Quartz)
220px-Oldf_Fashioned_Glass from
wikipedia

AMORPHOUS SOLIDS
 The constituent particles have no regular
arrangement and have short range order.
 No sharp melting point and melt over a range of
temperature.
 Isotropic :- Physical properties are same in all
directions.
 Considered as pseudo solids or super cooled
liquids.
 Irregular cleavage.
 Amorphous solids on heating become crystalline at
some temperature.
Ex: Glass objects of ancient civilization appear milky .
(Why……….)
 Amorphous solids have fluidity property.
Ex: Glass windows in old buildings appear thick at
bottom . (Why……….)
amormphous powder from wikipedia.jpg

CRYSTALLINE SOLIDS
 The constituent particles are orderly arranged .
 Have long range order and sharp melting
points.
 Anisotropic :- some of the physical properties
like refractive index are different in different
directions.
 These are considered as true solids.
 They undergo a clean cleavage.
 Crystalline solids have definite heat of fusion.
e.g. Diamond, Graphite, metals like Fe, Co, Cu
etc., Ionic compounds like NaCl, ZnS, KCl etc.
704px-Quartz_Brésil from
wikimedia.jpg

Iodine-unit-cell-3D-vdW
from wikimedia
Iodine
TYPES OF CRYSTALLINE SOLIDS
1.MOLECULAR CRYSTALLINE SOLIDS
Constituent particles are polar or non –
polar molecules or H-bonded molecules.
Force of attraction is dispersion force
or dipole- dipole interaction or hydrogen
bonding.
Low melting and boiling point.
Insulators
EX: Iodine

2.IONIC SOLIDS
Constituent particles are ions.
 Force of attraction is ionic bond .
High melting and boiling points.
Electrical insulators in the solid state
but conductors in aqueous solution
and molten state .
e.g: NaCl, LiF, MgO, ZnS, CaF2 etc. Sodium-chloride-unit-cell-3D fro
wikimedia
Sodium
Chloride

3.METALLIC SOLIDS
 Constituent particles are +vely
charged metal ions and free electrons.
 Force of attraction is metallic bond.
 High electrical and thermal
conductivity.
 Malleable and ductile.
 High melting and boiling point.
e.g.: Fe, Cu, Ag, Mg etc
Iron_from.jpg from wikimedia
Iron

4. COVALENT AND NETWORK SOLIDS
 Constituent particles are neutral
atoms.
 Force of attraction is covalent
bond .
 High melting point
 Insulators
e.g.: Diamond, quartz, SiC, AlN,
 Conductor :- Graphite Graphite-233436.jpg from
wikipedia
Graphite

SUMMARY
Classification of solids:-Crystalline and
amorphous
Classification of crystalline solids :-
Molecular , Ionic, Metallic and Covalent
solids .

QUESTIONS
1. Write a feature that will distinguish a metallic solid
from an ionic solid.
 2. Write a distinguish feature of covalent solid.
 3.Why graphite is good conductor of electricity although
it is a network (covalent solid)?
 4. What type of interactions hold the molecules
together in a polar molecular solid?

PART-2 OUTLINE
Crystal lattice and lattice points
Unit cell
Bravais lattices
Lattice points in unit cell

CRYSTAL LATTICE AND LATTICE POINT
 The regular arrangement of the
constituent particles (atoms ,ions
or molecules )of a crystal in three
dimensional space is called crystal
lattice or space lattice.
Each point in a crystal lattice is
called lattice point or lattice site.

UNIT CELL
Unit cell is the smallest
portion of the crystal lattice
which , when repeated in
different directions generates
the entire lattice .
Unit cell is characterized by 6
parameters.
(i) Edges (a, b ,c)
(ii)Angle between the edges .

CLASSIFICATION OF UNIT CELLS
Types :-
Primitive or simple Unit cells
Centered unit cells
PRIMITIVE UNIT CELLS:
When constituent particles are
present only at the corners of a
unit cell, it is called primitive
unit cell.

Classification of Unit cells
CENTERED UNIT CELLS:
Constituent particles are present at and other
other centred positions.
(i) BODY CENTERED UNIT CELL:
Constituent particles at each corners and one at
the centre of the body.
(ii) FACE CENTERED UNIT CELLS:
Constituent particles at each corners and other
at the centre of the faces.
(iii) END CENTERED UNIT CELL:
Constituent particles at each corners and other
at the centre of the alternate faces.

BRAVAIS LATTICES
On the basis of six parameters of unit cell , The total number of
possible unit cells (primitive and centred) in 3-dimensional lattice is
14.which are called Bravais Lattices.
S.NO. CRYSTAL SYSTEM EDGELENGTH BOND ANGLE EXAMPLES
1 CUBIC a=b=c α=β=γ=900
NaCl,KCl,diamond,Cu
2 TETRAGONAL a=b≠c α=β=γ=900
SnO2 ,CaSO4
3 RHOMBIC a≠b≠c α=β=γ=900
Rhombic S,KNO3 Ba2SO4
4 MONOCLINIC a≠b≠c α=γ=900,
β≠900
Monoclinic S,Na2SO4
5 TRICLINIC a≠b≠c α≠β≠γ≠900
K2Cr2O7,CuSO4 ,H2O
6 TRIGONAL a=b=c α=β=γ≠900
CaCO3,HgS
7 HEXAGONAL a=b≠c α=β=900
γ=1200
Graphite,ZnO,Ice

NUMBER OF ATOMS IN UNIT CELL
 Primitive or simple cubic
unit cell :-
Total no. of atoms for unit
cell
= 8 x 1/8 = 1 atom
 Body centred unit cell :-
Total no. of atoms for unit
cell
= 8 x 1/8 + 1= 2 atoms

NO. OF ATOMS IN A UNIT CELL
 Face centred unit cell :-
Total no. of atoms for unit cell
= 8 x 1/8 + 6x1/2 = 4 atoms

VISUALIZATION OF UNIT CELL
Courtesy – Next Education

SUMMARY
Crystal lattice and lattice point
Unit cell :- Primitive and Centred(bcc, fcc ,
ecc)
Bravais lattice:- 14 types(7 Primitive and 7
Centred )
No. of atoms of unit cell :- For scc-1atom,
bcc-2 atoms and fcc-4 atoms.

QUESTIONS
1. What is the significance of lattice point?
2. Explain how much portion of an atom
located at (i) corner an (ii) body centre of a
cubic unit cell is part of its neighbouring unit
cell.

• Review of previous session
• Closed packing in solids
• Voids in solids
PART -3 OUTLINE

Classification of solids:-Crystalline and amorphous
Classification of crystalline solids :- Molecular , Ionic,
Metallic and Covalent solids .
Crystal lattice and lattice points
Unit cell :- Primitive and Centred(bcc, fcc , ecc)
Bravais lattices:- 14 types(7 Primitive and 7 Centred )
No. of atoms of unit cell :- For scc-1atom,
bcc-2 atoms and fcc-4 atoms.
REVIEW OF PREVIOUS SESSION

 The constituent particles in solids are
close packed leaving minimum vacant
space .
 The packing pattern follows in one
dimension , two dimension and three
dimension .
 The no. of spheres neighbor to one
sphere is called its co-ordination no.
CLOSE PACKING IN SOLIDS

CLOSE PACKING IN SOLIDS
CLOSE PACKING IN ONE DIMENSION
• In one dimensional close packing arrangement , each sphere is in
contact with two of its neighbours .
• Coordination number is 2 .

CLOSE PACKING IN TWO DIMENSION
Square close packing in 2D(AAA….type ) :-
 Second row is placed adjacent to the
first row and so on .
 Co-ordination no. is 4 .
Hexagonal close packing in
2D(ABAB….type) :-
 second row is placed in the depressions
of spheres adjacent to first row .
 Co-ordination no. is 6 .

• When the second layer of spheres is placed in
the depressions in first layer , two types of voids
get formed.
PLACING OF SECOND LAYER ON FIRST LAYER
 Tetrahedral
voids
 Octahedral
voids

VOIDS IN SOLIDS
• The vacant space surrounded by
the spheres in the solids are called
voids.
Types:-
1. Tetrahedral voids :-
Holes surrounded by 4 spheres.
2. Octahedral voids :-
Holes surrounded by 6 spheres.

NUMBER OF VOIDS IN SOLIDS

Let the no. of close packed spheres = N
Then the no. of octahedral voids = N
 Then the no. of tetrahedral voids = 2N

Visualisation(voids in solid)
Courtesy:- university of north carolina

CLOSE PACKING IN THREE DIMENSION(AAA…
TYPE)
3D close packing from 2D square
close packed layers :-
• Spheres of the second layer are
placed just above the first layer and
so on
as AAA…..type .
• The lattice generated in simple
cubic lattice .
• Unit cell is primitive .
• e.g. polonium

3D close packing from 2D
hexagonal close packed
layers :-
placed in the depression of first layer .
• The third layer covers the tetrahedral
voids and forms ABAB…. Pattern and
forms hcp .
• Coordination no. is 12 .
CLOSE PACKING IN THREE DIMENSION

3D close packing from 2D
hexagonal close packed
layers :-
placed in the depression of first
layer .
• The third layer covers the
octahedral voids and forms
ABCABC…. Pattern and forms ccp .
• Coordination no. is 12 .
CLOSE PACKING IN THREE DIMENSION

Visualisation(close packing in solids)
Courtesy- Shiksha House

SUMMARY
• Close packing pattern in one , two and three
dimension in solids.
• Tetrahedral and octahedral void .The number
of tetrahedral voids are double the number of
spheres in the solid.

QUESTIONS
1. Distinguish between
a)hexagonal close packing and cubic close
packing.
b) Tetrahedral void and octahedral void

PART -4 OUTLINE
• Packing efficiency
• Calculation of packing efficiency in simple
cube ,bcc and fcc

RELATION BETWEEN EDGE LENGTH(a) AND
RADIUS(r) OF ATOM
scc fcc bcc

PACKING EFFICIENCY
The fraction of the total volume of the crystal occupied by the constituent
particles is called packing efficiency .
The fraction of the total volume of the crystal occupied by the constituent p
is called packing fraction or efficiency.
The packing fraction of the unit cell is same with that of crystal.
Packing fraction=
Volumeof atoms per unit cell
Volumeof unit cell
Packing fraction=
Number of atoms per unit cell Volumeof oneatom
Volumeof unit cell

Packing fraction =
3
4
3
3
n r
a


, a3
= volume of cubic unit cell
a = edge length or side length of the unit cell
r = radius of atom
n = no of atoms per unit cell

Packing efficiency of simple cubic unit cell :-
PACKING EFFICIENCY
a =2r
Volume of cubic unit cell = a3
PACKING EFFICIENCY
= volume occupied by four spheresx 100%
total volume of the unit cell
= 1 x (4/3)πr3
x
100%
(2r)3
= π x 100 = 52.36% = 52.4%
6

PACKING EFFICIENCY
Packing efficiency of face centred cubic unit cell :-
In ∆ABC AC2
=BC2
+AB2
b2
=a2
+a2
b= √2 a
If r is the radius of the sphere
b= 4r= √2 a
a=4r/√2
PACKING EFFICIENCY = volume occupied by four spheresx 100%
= 4 x (4/3)πr3
%
(2 √2r)3
= (16/3)πr3
%
(16 √2r)3
= 74%

Packing efficiency of body centred cubic unit cell :-
PACKING EFFICIENCY
In ∆ EDF
b2
=a2
+a2
b= √2 a
Now in ∆ AFD
c2
= a2
+ b2
= a2
+ 2 a2
= 3a2
c= √3 a
c = 4r
4r= √3 a
r = √3/4 a ,a = (4/√3) r
PACKING EFFICIENCY = volume occupied by four spheres x 100%
= 2 x (4/3)πr3
x100%
( (4/√3) r )3
= (8/3)πr3
x100% = 68%
64/3√3) r 3

COMPARISON OF PACKING EFFICIENCIES

Summary
• Packing efficiency :- scc - 52.4% , fcc – 74% ,
bcc – 68 % .
• packing efficiency is maximum in fcc unit cell.

Questions
1.Calculate the packing efficiency in case of a
metal crystal for body centred cubic .
2.What is the packing efficiency of a simple
cube?
3.Which unit cell has maximum packing
efficiency and what is the packing efficiency
percentage?

PART 5 OUTLINE
• REVIEW OF PREVIOUS SESSION
• IMPERFECTIONS IN SOLIDS
• TYPES OF POINT DEFECTS

REVIEW OF PREVIOUS SESSION
• Close packing pattern in one , two and three
dimension in solids.
• Tetrahedral and octahedral void .
• Packing efficiency :- scc - 52.4% , fcc – 74% ,
bcc – 68 % .

IMPERFECTION IN SOLIDS
Any deviation from perfectly ordered arrangement of
constituent particles In crystal lattice is called
imperfection in solids .
Ideal crystal After imperfection

Types of imperfections
There are 2 types of imperfections known in crystal
lattice.
• Point defect :- Arises due to disorder in the regular
arrangement of constituent particles around a
point .
• Line defect :- Arises due to disorder in the regular
arrangement of constituent particles in entire row .

TYPES OF IMPERFECTIONS
1. Impurity defect
Types of point defect :- 2.Stoichiometric defect
3.Non- stoichiometric defect
STOICHIOMETRIC DEFECT NON- STOICHIOMETRIC DEFECT
Vacancy defect Metal excess defect
Interstitial defect Metal deficiency defect
Frenkel defect
Schottky defect

IMPURITY DEFECT
• Arises when foreign atoms are present at
the lattice site in place of host atoms
generates impurity defect.
• When a little amount of SrCl2 is added to
NaCl, then at some lattice sites Na+
ions are
substituted by Sr 2+
maintaining electrical
neutrality .
• The cationic vacancies produced are equal
to number of Sr 2+
ions added .
SrCl2 added to NaCl

VACANCY AND INTERSTITIAL DEFECT
• These are seen in non ionic compounds.
• Vacancy defect :- Arises when some of the
lattice points are left vacant during the
crystal formation .
• Interstitial defect :- Arises when some of the
constituent particles accommodate in the
interstitial sites other than the lattice points.

SCHOTTKY DEFECT
• It is seen in ionic compounds.
• Equal no of cations and anions are missing
from their lattice sites generates schottky
defect.
• The vacancy defect(schottky) of ionic solids
decreases the density of solid
• Shown by the crystals with high
coordination no. and similar size of cation
and anion .
• e.g.NaCl, KCl, NaBr, AgBr

FRANKEL DEFECT
• It is seen in ionic compounds.
• In ionic solids in which the smaller ion i.e.
cation is dislocated from its normal site to an
interstitial site generates Frenkel defect.
• In the interstitial defect (Frankel) of ionic
solid ,density remains same .
• Shown by the crystals with low coordination
no. and large difference in the size of cation
and anion .
• e.g. ZnS, AgCl, AgBr, AgI.

METAL EXCESS DEFECT
By anion vacancies :-
It is seen in alkali halides.
• An anion may be missing from the lattice sites, and
the hole is occupied by an electron that maintains
electrical neutrality is known as
F-centre. ( Farbenzenter)
• The crystals become coloured due to excitation of
these unpaired electrons when they absorb energy
from visible light falling on the crystals .
• Excess of Li-makes LiCl crystals pink , K -makes KCl
crystals violet and Na –makes NaCl crystals yellow .

METAL EXCESS DEFECT
By extra cations :-
• Arises due to the presence .of extra cations in
the interstitial sites .
• Electrical neutrality is maintained by an electron
present in neighbouring interstitial sites.
• ZnO is white in colour at room temp. When ZnO
is heated, it loses oxygen and turns yellow.
ZnO Zn 2+
+ 1/2 O2 + 2 e-
e-
A
+
white yellow

SUMMARY
• IMPERFECTIONS IN SOLIDS :
• Line and point defects
• TYPES OF POINT DEFECTS –
• Vacancy defect, interstitial defect,Schottky
defect,Frenkel defect
• Impurity defect, stoichiometric defect, non
scoichiometric defect

INTEXT QUESTIONS
• What type of stoichiometric defect is shown by AgCl?
• What are F-centres?
• Which crystal defect lowers the density of solid?
• Which point defect in its crystal unit increases the density of a
solid?
• Why ZnO becomes yellow on heating ?

PART-6 OUTLINE
• Electrical properties of solids
• Magnetic properties of solids

ELECTRICAL PROPERTIES OF SOLIDS
Solid are classified as conductor, semi-conductor and insulator
on the basis of the magnitude of electrical conductivity
CONDUCTORS : The solids with conductance ranging between 104
to
107
ohm-1
m-1
are called conductors .Metals have conductivities in the order
107
ohm-1
m-1
are good conductors.
INSULATORS : These are the solids with very low conductivities ranging
between 10-20
to 10-10
ohm-1
m-1
SEMICONDUCTORS: These are the solids with conductivities in the
intermediate range from 10-6
to 104
ohm-1
m-1

VALENCE BAND THEORY
The conductivity
of solids depend
upon a number of
valence electron
available for atom
which can jump
from valance band
to conduction
band .

SEMICONDUCTORS
INTRINSIC SEMICONDUCTOR :-
Elements like Si and Ge
• Show too low electrical conductivity which
increases with temperature .
e.g. Si and Ge.
• Conductivity can also be increased by adding
appropriate amount of suitable impurity ,
process is called doping .
• Impurity is of two types :-
Electron rich impurity and
Electron deficit impurity. Silicon_(14_Si) from
wikimedia
Polycrystalline-germanium from wikimedia
Silicon
Germanium

SEMICONDUCTORS
EXTRINSIC SEMICONDUCTOR :-
• A doped intrinsic semiconductor is called extrinsic semiconductor .
• Types :-
1. n-type semiconductor (Doped with electron rich impurities )
2. p-type semi conductor (Doped with electron deficient impurities)

Visualization of n- type semiconductor
Courtesy- Physics4students

Visualization of p- type semiconductor
Courtesy – Physics4students

12-16 and 13-15 group compounds
• 12-16 Compounds: A semiconductor formed by
combination of group-12 and group-16 elements is
called 12-16 group compounds.
e.g: ZnS, CdS, HgTe, CdSe etc .
• 13-15 compound: A semiconductor formed by the
combination of group-13 and group-15 elements is
called 13-15 group compound.
e.g. AlP, Insb, GaAs etc.

MAGNETIC PROPERTIES OF SOLIDS
The magnetic properties of different solids are
due to orbital motion and spinning motion
of the electrons which are studied in term of
magnetic moments .

TYPES OF MAGNETIC SUBSTANCES
• Paramagnetic substance
• Diamagnetic substance
• Ferromagnetic substance
• Anti ferromagnetic substance
• Ferrimagnetic substance

Magnetic properties of solids
• Paramagnetic substance: -
• Weakly attracted by external magnetic field.
• Due to presence of one on more unpaired electrons.
e.g.: O2, Cu 2+
, Cr 3+ etc.
• Diamagnetic substance :-
• Weakly repelled by external magnetic field .
• Due to absence of unpaired electrons.
e.g. H2O, NaCl, C6H6 etc.

• Ferromagnetic substance: -
• Strongly attracted by external magnetic field and
show permanent magnetism.
• As the metal ions of ferromagnetic substance are
grouped into small regions called domains
e.g. Fe, Ni, Co, Gd, CrO2 etc

• Anti ferromagnetic substance :-
• Zero magnetic moment .
• Domain are arranged in opposite direction in
equal no..
e.g MnO.

• Ferrimagnetic substance : -
• Attracted by external magnetic field .
• Domains are aligned unequally in opposite
direction .
e.g. Fe3O4, MgFe2O4 (ferrite) etc

SUMMARY
PROPERTIES OF SOLIDS
• ELECTRICAL PROPERTIES point defect and line defect
• Impurity , Stoichiometric , Non- stoichiometric defect .
• – Band theory , Electrical conduction , n- and p- type
semiconductor
• MAGNETIC PROPERTIES OF SOLID
• – Para magnetism , Diamagnetism , Ferromagnetism ,
Anti ferromagnetism , Ferrimagnetism .

QUESTIONS
• How may the conductivity of an intrinsic
semiconductor be increased?
• What type of semi-conductor is obtained when
silicon is doped with arsenic?
• What is meant by ‘forbidden zone’ in reference to
the band theory of solid?
• What type of semi-conductor is obtained when
silicon is doped with Indium?

PART -7 NUMERICALS
NUMERICALS IN SOLID STATE
• Determination of the formula of the
compound
• Calculations involving unit cell dimensions.
• Calculation of fraction of metal ion in a non
stoichiometric metal oxides.

• A cubic solid is made of two elements X and Y.
Atoms Y are at the corners of the cube and X at
the body centre. What is the formula of the
compound?
Ans :-
Number of X atom per unit cell = 1
Number of Y atom per unit cell = 1/8 x 8 = 1
Formula of compound = XY
DETERMINATION OF THE FORMULA OF THE COMPOUND

• A cubic solid is made of two elements X and Y.
Atoms Y(anions) are at the corners of the cube and
X(cations) at present at face-centre of the cubic
lattice. What is the formula of the compound?
Ans :-
Number of X atom per unit cell = 1/2 x 6 = 3
Number of Y atom per unit cell = 1/8 x 8 = 1
Formula of compound = X3Y
DETERMINATION OF THE FORMULA OF THE
COMPOUND

CALCULATION OF THE DENSITY OF THE
UNIT CELL

• 1.Chromium metal crystallises with a body centred cubic
lattice The length of unit cell is found to be 287 pm.
Calculate atomic radius, the number of atoms per unit cell
and density of chromium. (Atomic mass of Cr = 52. g/ mol
Avogadro No. = 6.02 x 1023
)
• 2. Silver forms ccp lattice and X-ray studies of its crystals
show that the edge length of its unit cell is 408.6pm.
Calculate the density of silver( Atomic mass = 107.9 u)
• 3. Niobium crystallizes in body centered cubic structure. If density
is 8.55 gm/cm3
, calculate atomic radius of niobium using its
atomic mass 93u .
NUMERICALS

Silver crystallises in fcc lattice. If edge length of the
cell is 4.07 × 10–8
cm and density is 10.5 g cm–3
,
calculate the atomic mass of silver
Ans:
Given:
Edge length, a = 4.077 × 10−8
cm
Density, d = 10.5 g cm−3
The given lattice is of fcc type,
Thus the number of atoms per unit cell, z = 4
We also know that NA = 6.022 × 1023
/ mol
let M be the atomic mass of silver.
We know, d = zM/a3
NA
=> M = da3
Na / z
• = 10.5 x 4.077 × 10−8
x 6.022 × 1023
) / 4 = 107.13 g /mol

CALCULATION OF FRACTION OF METAL ION IN
A NON STOICHIOMETRIC METAL OXIDES.
• Analysis shows that nickel oxide has formula Ni 0.98O 1.00 .What fraction of
nickel exists as Ni2+
and Ni3+
ions?
A. Let the number of Ni2+
= x
The number of Ni3+
=(0.98-x)
sum of positive ions is equal to negative ions
2(x) + 3(0.98-x)= 2(1.00)
2x + 2.94-3x=2.00
X = 0.94 x= Ni2+
% of Ni2+
=0.94/0.98x 100=96%
% of Ni3+
= 100-96= 4%

THE SOLID STATE -nli-PPT.pptx IMPORTANT FOR STUDENTS

THE SOLID STATE -nli-PPT.pptx IMPORTANT FOR STUDENTS

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