Question
How will you distinguish between the following pairs of terms:
Crystal lattice and unit cell?
Solution
How will you distinguish between the following pairs of terms:
Crystal lattice and unit cell?
How will you distinguish between the following pairs of terms:
Tetrahedral void and octahedral void?
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.
Explain the basis of similarities and differences between metallic and ionic crystals.
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. |
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