General characterstics of solid state
- Solids have definite mass,volume and shape due to the fixed position of their constituent particles.
- Solids have short intermolecular distances and strong intermolecular forces.
- The constituent particles of solids (atoms, molecules or ions ) have fixed positions and can only oscillate about their mean positions.
- Solids are incompressible and rigid.
Types of solid states– Based on the arrangement of constituent particles,
- Crystalline Solids
- Amorphous solids
- Definite characteric geometrical shape
- Irregular shape
- Melt at a sharp and characteristic temperature
- Gradually soften over a range of temperature
- When cut with a sharp edged tool , they split into two pieces and the newly generated surfaces are plain and smooth
- When cut with a sharp edged tool, they cut into two pieces with irregular pieces
- Anisotropic (physical properties have different value in different directions) in nature
- Isotropic (physical properties have same value in different directions) in nature
- True solids
- Pseudo solids or supercooled liquids
Order in arrangement of constituent particles
- Long range order
- Only short range order
Heat of fusion
- They have a definite and characteristic heat of fusion
- They don’t have definite heat of fusion
- Classification of crystalline solids on the basis of nature of intermolecular forces
Types of solids
Type of forces
Properties and examples
- Lattice points are occupied by +ve and -ve ions held together by strong coulombic (Electrostatic) forces
- High lattice energies,
- Hard but brittle,
- High meting and boilong point,
- Insulator in solid state but good condcutors in molten state and in aqueous solutions
- E.g. NaCl,MgO,ZnS
Covalent or network solids
- Lattice point are occupied by atoms held by a network of covalent bonds
- Extremely high mp
- Very hard and brittle,
- insulator expect graphite,
- In metals, the array of lattice points is occupied by +ve ions. The outer electrons are loosely held
- Hard but malleable and ductile,
- Fairly high melting point
- Good conductor of electricity in solid state as well as in molten state
- E.g-All metals and alloys
Molecular solids (polar, non polar and hydrogen bonded)
- Lattice positions are occupied by molecules and are held together by weak van der waals forces
- Low melting points
- E.g.Solid CO2,HCl,Ice
- A regular three dimensional arrangement of the constituent particles of a crystal in space is called crystal lattice
- It is a smallest portion of a crystal lattice which when repeated in different directions, generated the entire lattice
- A unit cell in characterised by six parameters-three edges a,b and c and angles b\w the edges, α,β and γ.
Types of unit cells
- Primitive unit cells
Constituent particles are present only on the corner positions of a unit cell.
- Centred unit cell
Unit cell contains constituent particles at corners as well as at some other positions
There are a 3 type of centred unit cell.
One Constituent particles at body centre besides the ones that are at its corners.
One constituent particle present at the centre of each face besides the ones that are at its corners.
One constituent particles present at the centre of ant two opposite faces besides the ones that are at its corners.