How will you distinguish between the following pairs of terms:
Crystal lattice and unit cell?

Solution

Question 114

How will you distinguish between the following pairs of terms:
Tetrahedral void and octahedral void?

Solution

Question 115

Solution

Solution:

(i) One unit cell of a face-centered cubic has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

(ii) One unit cell of face-centered tetragonal has 8 lattice points are corners and 6 lattice points at faces, total 14 lattice points.

(iii) One unit cell of body centered has 8 lattice points are corners and 1 lattice points at faces, total 9 lattice points.

Question 116

Solution

The similarities and differences between metallic and ionic crystals are described as below:

Characteristics		Ionic crystals	Metallic crystals
1.	Constituent particles	cations (positive ions) and anions (negative ions)	Positive ions and mobile electrons.
2.	Binding forces	Strong electrostatic forces (electro valent bonding)	Electrical attraction between positive ions and mobile electrons (metallic bonding)
3.	Physical properties	Hard and brittle; high m.p. and b.p. good conductors of heat and electricity in molten state and aqueous solution, high heat of fusion.	Hard but malleable, high m.p., very good conductors of heat and electricity in solid and molten state, moderate heats of fusion.