Solid State 12 updated syllabus 2020 Maharashtra State board

1. Chemistry
XII
Solid State
Presentation
By
Mr. Barache S.B.
M.Sc B.Ed

2. Solid state
Contents
 Introduction
 Types of solids
 Classification of crystalline solids
 Crystal Structures
 Cubic systems
 Packing of particles in crystal lattice
 Packing efficiency
 Crystal defects or imperfections
 Electrical properties of solids
 Magnetic properties of solids

3. Characteristics of solid:-
1. Solid has fixed mass, volume , shape and density
2. Most of solids are hard , incompressible and rigid.
3.Solids are denser than liquid or gaseous state
4. As compared to liquid or gaseous state, solid states have stronger
intermolecular forces of attraction between the constituent particles
5. The constituent particles of solid are held tightly by intermolecular
forces of attraction hence the particles cannot change their position.
Solid
Crystalline Amorphous
Ionic Metallic Covalent Molecular
Polar Non-polar Hydrogen Bonded

4. Distinguish between Crystalline and Amorphous solids:-

5. Isomorphism:-
Two OR more substances having the same crystal structures are
said to be isomorphous
e.g. NaF and MgO = 1:1
NaNO3 and CaCO3 = 1:1:3
Polymorphism:-
A single substance that exists in two OR more forms of crystalline
structure is called as polymorphous
e.g. Carbon having two polymorphic forms that is diamond and graphite
Sulphur having monoclinic and rhombic polymorphic forms.
Crystalline Solids
Molecular crystals
Ionic crystals
Metallic crystals
Covalent network crystals

7. #Crystal Structures :-
The ordered three dimensional arrangement of particles in a crystal is
described using two terms that is Lattice and Basis
Lattice :- A geometrical arrangement of points in a three dimensional periodic array.
crystal lattice is also called space lattice of crystal.
Basis :-
The crystal structures is formed by associating ev very lattice point with an
assembly of atoms or molecules or ions, which are identical in composition,
arrangement and orientation, is called as Basis

8. Differentiate betn crystal lattice and unit cell:-
Sr.
No.
Crystal Lattice Unit Cell
1 The regular arrangement of
constituent particle in the three
dimensional space
Smallest repeating structured unit of
crystalline solid
2 It is made up from no. of unit cell It is fundamental unit of crystal lattice
3 It can divided into no. of unit cell It cannot further divided
4 Crystal lattice can be prepared
experimentally
It is imaginary part
5 Macroscopic in nature It is microscopic nature

9. Unit cells :- The smallest repeating structural unit of a crystlline solid is called
as unit cell
Base centred unit

10. #Bravais lattice:-
There are fourteen bravais lattices (unit cells) for each of the seven
crystal system.

11. Lattice Types Edge Length
Angles
between faces
Examples
Cubic Primitive, Body-
centred, Face-
centred
a = b = c α = β = γ = 90
°
NaCl, Copper
and ZnS
Tetragonal Primitive, Body-
centred
a = b ≠ c α = β = γ = 90° White tin, SnO2,
TiO2 and CaSO4
Orthorhombic Primitive, Body-
centred, Face-
centred , End-
centred
a ≠ b ≠ c α = β = γ = 90° Rhombic
Sulphur,
BaSO4 and KNO3
Hexagonal Primitive a = b ≠ c α = β = 90
°
and γ
= 120°
Graphite, ZnO
and CdS
Rhombohedral Primitive a = b = c α = β = γ ≠ 90° CaCO3 ( Calcite)
and HgS
(cinnabar)
Monoclinic Primitive, End-
centred
a ≠ b ≠ c α = γ = 90° β ≠
90°
Sulphur
Triclinic Primitive a ≠ b ≠ c α ≠ β ≠ γ ≠ 90
0
H3PO3 , CuSO4.5
H2O

12. #Cubic system:-
There are three kinds of unit cells in cubic system.
 Simple or Primitive cubic (sc)
 Body – centred cubic unit cell (bcc)
 Face – centred cubic unit cell (fcc)
#Number of particles in cubic unit cells:-
1) simple cubic unit cell (sc):- particle
2) Body-centred cubic unit cell(bcc):- particles
3) Face-centred cubic unit cell(fcc):- particles

13. Relationship between molar mass, density of the substance and unit cell
edge length:-
 Mass of unit cell = m × n ( mass of 1 particle is ‘m’ & if the no. of particle present is
unit cell is ‘n’)
 Volume of unit cell = a3 ( edge length of unit cell is ‘a’)
Therefore,
density (ρ)= = ------------1
 Molar mass of the substance (M) = m × NA ( where NA is Avogadro’s Constant)
m = ----------2
Combining equation no. 1 & 2 ,we get
( density )

14. #Packing of particles in crystal lattice:- The packing of particles in crystal,
the individual particles are treated as hard spheres.The closeness of
particles maximize the interparticle attractions. The larger the
coordination number, the closer are the spheres to each other.
a) close packing in one dimension
b) close packing in two dimension
c) close packing in three dimension
a) Close packing in one dimension:-
b) Close packing in two dimension:-
i) square close packing :- AAAA…..type

15. ii) Haxagonal close packing:- ABABAB……type
c) Close packing in three dimension:-
i) Stacking square close packed layers:- AAAA……type
A
A
A
A

16. ii) Stacking of two hexagonal close packed:-
iii) Placing third hexagonal close packed:-
(a)ABABAB…..type and (b) ABCABC…….type

17. #Coordination number:-
The number of neighbouring spheres that touch
any given sphere is its coordination number.
coordination number is 4.
coordination number is 6.

18. #Voids:-
Voids in solid states mean the vacant space
between the constituent particles in a closed packed
structure.
Let the number of close packed spheres be N, then,
The number of octahedral voids generated = N
The number of tetrahedral voids generated = 2N

19. #Packing Efficiency:-
Packing efficiency is the fraction or a percentage of
the total space occupied by the spheres (particles).
Packing efficiency:-
There are four steps to determine the
packing efficiency of given crystal in their unit cell.
Step I :- Radius of sphere
Step II :- Volume of sphere
Step III :- Total Volume of particles
Step IV :- Packing Efficiency

20. A) Packing efficiency of metal crystal in simple cubic lattice:-
Step I :- Radius of sphere
r = ---------1
Step II :- Volume of sphere
Step III :- Total volume of particles
simple cubic unit cell contains only one particle,
Volume occupied by particle in unit cell =
Step IV :- Packing efficiency:-
= =
Thus, in simple cube lattice ,52.36% of total space is occupied by particles and
47.64% is empty space, that is , void volume.

21. B) Packing efficiency of metal crystal in body-centred cubic lattice:-
Step I :- Radius of sphere
Step II :- Volume of sphere
Step III :- Total volume of particles
Body-centred cubic (bcc) contains 2 particles. Hence , volume
occupied by particles in bcc unit cell
Volume occupied by particle in unit cell =
Step IV :- Packing efficiency:-
Thus, 68% of the total volume in bcc unit lattice is occupied by atoms and 32% is empty
space or void volume.

22. C) Packing efficiency of metal crystal in face-centred cubic lattice:-
(fcc or ccp or hcp )
Step I :- Radius of sphere
Step II :- Volume of sphere
Step III :- Total volume of particles
Face-centred cubic (fcc) contains 4 particles. Hence , volume occupied by
particles in fcc unit cell
Step IV :- Packing efficiency:-
Thus, 74% of the total volume in fcc ( ccp or hcp)unit lattice is occupied by atoms and 26% is
empty space or void volume.

23. Crystal defects OR imperfections:-
Some imperfection in formation of crystal lattice is known as defect.
#There are three types of defects.
1) Point defects
2) Line defects
3) Plain defects
# Point Defects:-
These defects are irregularities produced in the arrangement of
of basis at lattice points in crystalline solids.
There are three major classes of point defects.:-
A) Stoichiometric point defects
B) Impurity defects
C) Non-stoichiometric point defects

24. A) Stoichiometric point defects:-
Stochiometric defects are those in which the no. of positive and negative
ions is exactly in the ratios indicated by their chemical formula.
There are four types of stoichiometric point defects.
a) Vacancy defects
b) Self interstitial defect in elemental solid
c) Schottky defect
d) Frenkel defect
a) Vacancy defects:-
In crystallization of a solid , a particle is missing from its regular
site in the crystal lattice. The missing
particle creates a vacancy in the lattice
structure. Thus, some of the lattice
sites are vacant because of missing
particles as shown in figure, the crystal
is, then ,said to have a vacancy defect.

25. b) Self interstitial defect in elemental solid:-
Interstitial sites in a crystal are the spaces or voids in
between the particles at lattice points. When some particles of a crystalline
elemental solid occupy interstitial sites in the crystal structure, it is called
Self interstitial defects.
i) Extra particles increase the total
mass of substance without increasing
volume. Hence its density increases.
ii) The displacement of particle a
vacancy defect is created at its
original regular lattice site. At the
same time interstitial defect
results at its new position
Density remains as it is.

26. c) Schottky defect:-
Sometime during crystallization some of place of the
constituent particles remain unoccupied and the defect is generated is
called vacancy defect.
The defect caused by due to vacancies by absence of
anions and cations in the crystal lattice is called Schottky defect.
Due to the vacancies in the some of the sites of ions the observed
density of the crystal found to be lower than expected density. This defect
is observed in solids which cation and anion almost equal size.
e.g. KCl, NaCl, CsCl, AgBr
Schottky defect appears generally
in ionic compounds having high
co-ordination number of anion and
which radius r+/r— is not far below
unity also have high degree of ionic
character.
Schottky defect occurs in almost type
in ionic crystal
however Schottky defect appears more than Frankel defect.

27. d) Frenkel defect:-
When cation or anion from ionic solid leaves it regular site
and moves to occupy place between the lattices sites called as Frenkel
defect.
This defect is generally observed in case of relatively smaller
cation which can fit into interstitial space and hence produce the defect.
The presence of this defect does not alter the density of solid. This defect is
common when the difference in ionic radii of two participating ions is
large.
In this defect dielectric constant of solid increases.
e.g. AgCl, AgBr, ZnS, AgI, CaF2
Frenkel defect occurs in ionic
Compounds with large difference
between sizes of cation and anion.
The ions of ionic compounds
must be having low coordination
number.

28. B ) Impurity defects :-
The impurity defect occurs when regular cation of the crystal is
replaced by some different cation.
i) The different cation sometimes occupy
interstitial site. It impurity is substituted
in place of regular cation. It is called
substitution impurity defect.
ii ) The impurity is present
in interstitial position then
it is called interstitial
impurity defect.
e.g. Alloys
I. Alloys are form by substitution defects
II. Brass is substation alloy formed by substituting copper metal by zinc metal
in ratio 3: 1
III. Stainless steel in an interstitial alloy formed by introducing carbon atom
impurity ,pure iron is soft malleable ductile stainless steel is hard stronger
less ductile shiny and bright in appearance

29. C) Non-stoichiometric point defects:-
Nonstoichiometric defect arises when the ratio of number of
atoms of one kind to that of other kind or the ratio of number of cations to anions
becomes different from that indicated by its chemical formula
i.e. Stoichiometry of the compound is changed.
There are two types of nonstoichiometric defects.
i) Metal deficiency defect
ii) Metal excess defect
i) Metal deficiency defect:-
This defect is possible only in compounds of metals that show variable
oxidation states.

30. ii) Metal excess defect:-
There are two types of metal excess defects.
a) A neutral atom or an extra positive ion occupies interstitial position:-
b) By anion vacancies(colour or F-centres)
This type of defect imparts
colour to the colourless crystal.
The anionic site is occupied by
an unpaired electrons is called
F-centres. This centre are
responsible for colour of compounds.