Solid state

1.The Basic Concepts

By strong intermolecular forces.

Constituents have fixed position can only oscillate

about their mean positions.

2.Characteristic property of solid state

*In solid state particles are very closely packed and

Definite geometry with very small void.

*In solid state particle are not able to move randomly.

*Solid have high and sharp melting point.

*In solid state intermolecular force are very strong.

*In solid state particle are incompressible and rigid.

*In solid state particle are high density.

3.Solid state are present in two type.

(A) Crystalline solid

(B) Amorphous solid

(A)Crystalline solid =In crystalline solid particles are

Orderly arrange and having sharp melting point.

Example=NACL, Quartz etc.

(B) Amorphous solid=An amorphous solid

Constituent particle are irregular in shape and

Short range order.

Example=Quart, glass, plastic etc.

4.Different parts of crystalline solid.

(A) Ionic solid=These are formed by combination of

High electropositive ion.

Example- NaCl etc.

5.Characteric property of ionic solid.

(I)They have high melting point and boiling point

And ions are not free to move.

(II) In solid state they are electrically insulator.

(III) In molten state or dissolved state ion are free

Free to move and they are electrically

Conductor.

(B) Metallic solid = These are formed by a combination of atom are bounded by metallic bond.

Example-Na, Al, Cu

(C)Covalent or network solid = These are formed by the sharing of valance electron between two non-metal Atom resulting in the formation of covalent bond.

*They are insulator and do not conduct electricity.

*Diamond, graphite and silicon carbide are typical example of covalent solid.

*Graphite are conductor due to presence of free electron.

(D)Molecular solid

*It is of three type-

(I)Non-polar molecular solid= In this solid atom or molecular are held by weak dispersion force or London force.

(II)Polar molecular solid= It is formed by polar molecular bond on formed by dipole-dipole interaction.

Example-HCL, NH3 etc.

(III)Hydrogen bonded molecular solid= It is formed by highly electronegative element (F, O, N) and hydrogen atom is called hydrogen bonded molecular solid.

Example- HF, H2O etc.

7. Crystal lattice and unit cell.

*Crystal lattice=The three- dimensional arrangement of constituent particles in the crystal i.e. each particle is arranged as a point is called crystal lattice.

*There are only 14 possible three- dimensional lattice are called Bravais lattice.

*Unit cell = Unit cell is the smallest portion of a crystal lattice. A unit cell is characterized by its dimension three edge a, b and c.

*These Edge may or may not be mutually perpendicular to each other.

7. Primitive and centered unit cell.

(a) primitive unit cell= when constituent particles are present only on the corner position of the unit cell is called primitive unit cell.

(b) Centered unit cell= When the unit cell contain one or more constituent particle are present at position _{unit cell other then corner is called centered}

8.Centered unit cell are of three type-

(I) Body centered unit cell (B.C.C) = Such a unit contain one constituent are present on body center is called body center unit cell.

(II) Face centered unit cell (F.C.C) =Such a unit cell contain one constituent particles are present at the of each face.