Solid state

Solids :-

Solids are the chemical substances which are characterized by define shape and volume,  rigidity, high density, low compressibility. The constituent particles (atoms, molecules or ions) are closely packed and held together by strong inter particle forces

Types of solids :-

Their are two types of solids :-
1)Crystalline solid
2)Amorphous solid

Difference between crystalline and amorphous solids :-

Crystalline solid	Amorphous solids
1 These have definite and regular arrangement of the constituent particles in space.	These doesn’t have any regular arrangement of the constituent particles in space.
2 These are true solids.	These are super cooled liquids or pseudo solids.
3 These have long order arrangement of the particles.	These have short order arrangement of particle.
4 These are anisotropic in nature, i.e., their physical properties are different in different directions.	These are isotropic in nature i.e., their physical properties are same in all the directions.
5 They have sharp melting points.	They melt over a certain range of temperature.
6 They undergo a clean cleavage when cut.	They undergo irregular cleavage when cut.

Types of crystalline solids:-

Character	Ionic solids	Covalent solids	Molecular solids	Mettalic solids
constituent particles	Positive and negative ions	Atoms	Molecules	Positive metals ions(kernels) and free electrons
Bonding Forces	Electrostatic Attraction	Covalent	Vander walls dipole dipole	electrostatic attraction between Positive ion and negative species
Melting Point	High Melting point	Very high melting point	Low melting point	Moderate to high melting point
Hard/Soft	Hard and Brittle	very hard	very soft	hard and soft
Conductance	Conductor in aqueous solution or in molten state	Non Conductor	Insulator conductor	Good conductor
Example	Nacl and Caf2	Diamond and silica	H2O and CO2	CU and FE

Structure determination by X-ray diffraction-Bragg's equation :-

Bragg equation states that there is a definite relationship between the angle at which a beam of X rays must fall on the parallel planes of atoms in a crystal in order that there be strong reflection, the wavelength of the X rays, and the distance between the crystal planes :  sin Θ = nλ / 2d where Θ is the angle between the incident or the reflected beam and the crystal plane, λ is the X-ray wavelength, d is the crystal plane separation, and n is any integer

Unit cell :-

The smallest geometrical portion of the crystal lattice which can be used as repetitive unit to

build up the whole crystal is called unit cell

Types of unit cell

1)Simple or primitive unit cell :-

In the simple unit cell particles are present only at the corners of the crystal :-

Number of atoms in simple cubic lattice is equal to 1 and can be calculated as below:-

 8 atoms are present at corner
so,Number of atoms = 8*1/8=1

2)Face centred unit cell :-

In this particles are present at corners as well as at every face of the crystal.

Numbers of atoms present in FCC:-

Number of atoms presnt at corners=8
Number of atoms present at the faces=3
  so total no atoms= 8*1/8+6*1/2=4

3)Body centred unit cell :-

In this particle are present at the corners as well at the body center
Number of atoms in BCC is eqaul to :-

Number of atoms presnt at corners=8
Number of atoms present in the body=1
  so total no atoms= 8*1/8=1+1=2

4)End centered unit cell :-

In this particles are present at all the corners of the crystal as well at the ends of crystal

Number of atoms present in end centered unit cell:-
Number of atoms presnt at corners=8
Number of atoms present at the ends=2
  so total no atoms= 1+1=2

Number of particle per unit cell of a crystal:-

Seven crystal system :-
There are about 230 crystal forms, which have been grouped into 14 types of space lattices,
called Bravais Lattices, on the basis of their symmetry and seven different crystal systems on
the basis of interfacial angles and axes.

Packing Fraction:-

1)Packing fraction in a simple cubic unit cell:-

Consider radius of sphere is = r
and Edge length of unit cell =a
As sphere are touching each other so edge lengt will be equal to 2r
                   
No. of sphere per unit cell= 1
Volume of sphere = 4/3πr3
Volume of cube =a3= (2r)3 = 8r3
Packing fraction (PF)=Percentage occupied = 52.4%

2)FCC Packing fraction:

3)BCC Packing Fraction:-

so packing fraction in Body centered unit cell = 68%

Cordination number:-



Void or space or holes

Density of unit cell

The structure of ionic crystals

Imperfections in solids

Point defects:-

1)Stoichiometric defect :-

In these defects equal number of cation and anion get missing from the crystal so the ratio of anion and cation remains same as the Stoichiometry of the substance not changed.
These are further classified as:
1)Vacancy defects: - These happens when some crystal site is vacant and it results in dcrese in density.
2)Interstitial Defects: - When some constituent particles present in the interstitial side, it increase the density of the crystal.
3)Schottky Defects:- If in a ionic crystal +ve or –ve ions missing their lattice sites so that electric neutrality is maintained
                 Ex: NaCl, KCl, CsCl, AgBr.
4)Frenkel Defect: - If an ion missing their lattice site (causing vacancy or hole their) and comes in the interstitial side, so maintain electric neutrality or Stoichiometry of the crystal is called Frenkel defect.
                 Ex: ZnS, AgCl, AgBr, AgI.

2)Impurity defect

3)Non stoichiometric defect

Classification of solids on the basis of electrical conductivity

semiconductors

Intrinsic semiconductors

Extrinsic semiconductors

Magnetic properties of solids:-

Diamagnetic substances :- Substances which are weakly repelled by external magnetic field is called as diamagnetic substances.

e.g:-Nacl

Paramagnetic substances :-

Substances which are attracted by external magnetic field is called para magnetic substances

Ferromagnetic substances :- substances which show permanent magnetism even in the absence of magnetic field is called feeomagnetci substances

Anti ferromagnetics substances :-

Substances which are expected to posses’ paramagnetism and ferromagnetism on the basis of magnetic moments of the domains but actually they posses Zero magnetic moment are called anti- ferromagnetic substances.

Ferrimagnetic substances :-
Substances which are expected to posses large magnetism on the basis of magnetic moments of the domains but actually have small net magnetic moment are called ferrimagnetic substances.