Space Lattice: 
An infinite three dimensional array of points showing how atoms (or) molecules are arranged in a crystal is known as space lattice. The points are known as lattice points.

The length of the side of the unit cell of the metal is 353.55 pm.
For fee unit cell, a =(2√2) x r
= 2 x 1.414 x 125
= 353.55pm.

(I) Diamond has network structure, while sulphur does not.
(II) Due to this, particles of carbon are held at their positions firmly which makes diamond hard, brittle with extremely high melting point.

The defects which are caused by missing or misplaced atoms or ions in the crystal.

The empty spaces present between the metal atom or the ions when they are packed within the crystal are called voids.

A solid is said to be amorphous if its constituent particles are not arranged in a regular fashion

Frenkel defect

Gallium.

Total number of atoms per unit cell in a fcc structure = 4 atoms.

(i) When a solid is heated, vacancy defect can arise.
(ii) A solid crystal is said to have vacancy defect when some of the lattice sites are vacant
(iii) Vacancy defect leads to a decrease in the density of the solid

(i) In ionic compounds, electricity is conducted by ions.
(ii) In solid state, ions are held together by A strong electrostatic forces and are not free to move about within the solid.
(iii) Hence, ionic solids do not conduct electricity in solid state
(iv) However, in molten state or in solution form, the ions are free to move and can conduct electricity.

ZnS exhibits Frenkel defect.

(i) The intermolecular forces of attraction that are present in solids are very strong.
(ii) The constituent particles of solids have fixed position.
(iii) Hence, solids have a definite volume.