Solid state.

    1. Solid state.

Solid :

 - solid is the state of matter in which constituent particles are bonded with strong force of attraction.

1) Isomorphism :- 

1) Two or more substances having the same crystal structure are said to be Isomorphism.

2) In these substances, the chemical composition has the same ratio.

2) Polymorphism :- 

1) Single substance exist in two or more forms or crystalline structure is said to be polymorphism.

2) Polymorphs of structure formed in different conditions.

3) Example : Calcite and aragonite are two forms of calcium carbonate.

4) When it occur in element is called as allotropy.

Classification of crystalline solids :-

1) Ionic solid - 

1) Constituent particles are charged ions.

2) Both are bonded with each other by columb force.

3) Particles are held by electrostatics force of attraction.

4) They are hard/brittle with high melting point.

5) They are non-conductor at solid state and become good conductors when dissolved into liquid.

6) Example :- NaCl, KCl, etc.

2) Covalent network crystal :-

1) The constituent particles in covalent network solid atoms.

2) Constituent particles are linked with continuous covalent bond.

3) Result is 3-D network forms gaint molecules.

4) Entire crystal is single molecule.

5) Very hard and incompressible with high melting and boiling point.

6) These are poor conductors because, electron's are localised in covalent bond and are non-motile.

3) Molecular crystal :-

1) Substances like Cl2, CH4, H2 on solidification give molecular crystal.

2) Constituent particles are molecules. [Unbounded single atom]

3) They are held by various intermolecular forces of attraction.

4) Having low melting point with soft substance.

5) They are poor electrical conductors and are good insulators.

4) Metallic crystal :-

1) Formed by atoms of same metallic element and bonded with metallic bond.

2) In metal, valence electrons are the localised over the entire crystal.

3) Attractive interactions between cation and mobile electron constituent metallic bond.

Properties of metallic crystal :-

1) metals are malleable, that is they can be hammered into thin sheets.

2) metals are ductile, that is they can be drawn into wires.

3) Metals have good electrical and thermal conductivity.

Crystal structure :

- crystal is described in two terms :

 I) lattice :- it is an ordered array  of point describing the arrangement of particle that form a crystal.

II) Basis :- an atom of group of atom which is associated with a crystal lattice to form crystal.

Unit cell :- 

1) The smallest repeating structure unit of a crystalline solid is called Unit cell.

2) It is the smallest part of a crystal that repeat regularly to translation in 3D creates whole structure.

3) Structure of unit cell depends upon the structure of crystal.

4) The dimension of unit cell is defined by A, b and C.

5) A, B and C  = axis.

 Alpha, beta, and gamma = angle between these angles.

Types of unit cell :-

1) primitive / simple unit cell :- 

The constituent particle are present at the corners only.

2) Body-centred unit cell :-

One constituent particle is present at centre of its podi in addition to the corner particle.

3) Face-centred unit cell :-

Consists of particle as the centre of each faces in addition to corner particle.

4) Base-centred unit cell :-

Unit cell consists of particle at the centre of any two of its opposite faces in addition to corner particle.

Crystal system :-

1) There are only 14 ways to form different type of a lattice is by placing particles.

2) Hence, there is only 14 types of lattices. I.e  this 14 letters is called as bravia lattice.

3) 14 bravias lattice  is also called as 14 unit cell.

 4) It also gives 7 crystal system. they are as follows:

1) Cubic.

2) Tetragonal.

3) Orthorhombic.

4) rhombohedral.

5) Monoclinic.

6) Tri-clinic.

7) Hexagonal.l

Cubic system :

There are 3 kinds of unit cell in cubic system.

I) Simple cubic unit cell :- 

Having particle at each 8 corner of cube.

II) Body centred unit cell :-

Having particle at each 8 corner and also at the centre of cube.

III) Face centred cubic unit cell :-

Having particle at each 6 face.

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