class 12 Chapter 1 Solid State Chemistry Notes

 

Chapter 1

Solid state

General characteristic of solid:-

       I.        Solid is defined as that formed of matter which have rigidity and have definite shape and definite volume.
      II.          Constituent particle are very closely packed solid are in comphensible.

Solid are further classified into two parts:-

Crystalline

•        I.          Constitute particle are arranged in regular manner and have long range orderness.

      II.          They have sharp(exact) melting point.
    III.          They undergo a clean cleavage.
    IV.          There are anisotropic in nature.
     V.          Nacl, Zns, crystall

Amorphous

       I.          Constituent particle are arranged in irregular manner.
      II.          They melt over range of temperature.
    III.          They undergo an irregular cut.
    IV.          There are isotropic in nature.
     V.          Glass, plastic, rubber

Anisotropic:-

When some physical properties like electrical conductivity, refractive index etc. are measured in different direction in crystalline solid there values are different.

Since, arrange of particles is different in each direction. This properties known as anisotropic.

In case of amorphous- all these properties same in each direction and this is known as isotropic.

 

 

 

 

For crystall

 

Super cooled liquid or pseudo solid:-

Glass window panes of some very old houses are formed to thicker and the bottom thinner at the top such type of solid are called pseudo solid or super cooled liquid.

Classification of crystalline solid:-

 

Molecular solid:-

       I.          Non polar molecular solid:-
They are formed by non polar covelent bond.
Example- H₂, cl₂,I₂

Ø  In these solid atom are arranged by weak dispersion force or London force. That is Why they have low melting point.

Ø   And they are very soft.

Ø  Poor conductor of electricity.

     II.          Polar molecular solid:-

Ø  The molecular like HCL, SO_2, HB_r are formed by polar covelent bond.

Ø  Force present is dipole dipole intraction and have more melting point then non polar molecule.

    III.          Hydrogen bonded molecule:-

Ø  The molecules of such solid contain polar covelent bond between H, F, O, N atom.

Ø  Force present is H-bond force of attraction.

Ø  Example:- H₂O(ice)

Ionic solid:-

Ø  Constituent particle are ions.

Ø  Force present is strong electrostatic force of attraction.

Ø  Heigh melting point and boiling point.

Ø  In molten state due to presence of free ions these solid conduct electricity.

Ø  Example:- NaCl

Metallic solid:-

Ø  Constituent particle are metal surrounded by large no. of free electron.

Ø  These solid are ductile in nature.

Ø  These are good conductor of electricity.

Covalent or network solid:-

Ø  Constitute particle are atom.

Ø  Covalent bonding is present and this solid have 3-D network structure are hard.

Example:- diamond, graphite

Ø  Graphite is also example of covalent solid but it is very soft and slippry.

Ø  It is used as a lubricant and also it is used as good conductor of electricity.

Crystal lattices and unit cells:-

Regular 3-D arrangement of the particles in space is called crystal lattice.

Unit cell-

It is the smallest portion of crystal lattice which when repeated in different direction generate the whole lattice.

There are two characteristic of unit cell:-

§  its dimension along the three-edges that is a, b, & c.

§  angle alpha between b&c beta between a&c gamma between a&b

§ 

 

Unit cells are basically divided into two categories:-

       I.          Primitive unit cell-  

When constituent particles sre present only the corner position of unit cell

     II.          Centred unit cell-

When unit cell contain constituent particles other then corner in addition to particles at the corner.

Centred unit cell are further devided into three part:-

       I.          Body centred unit cell-

In this unit cell atom are at the corner as well as centre of the unit cell.

      II.          Face centred unit cell-

Atom are present at the corner as well as centre of each face.

    III.          End centred  unit cell-

One constituent particle present at any two opposite face as well as particles are at the corner.

Seven primitive unit cell:-

Number of atom in a unit cell:-

Primitive(simple) cubic unit cell:-

In primitive cubic unit cell

Corner = 1/8

Total corner = 8

Total no. of atom = 8*1/8 =1

Body centred cubic unit cell:-

Atom corner + centre of unit cell

Corner = 8

Centre = 1/8

Total = 1/8*8 = 1

Centre = 1    ,    corner = 1  ---- 1*1=1

Face centred unit cell:-

Corner + centre of face

Corner = 8

Contribution of each atom = 1/8

Total atom 8*1/8 = 1

Total face = 6

Contribution of each atom = ½

½*6 = 3

Total atom = 1+3 = 4