Crystalline Solids

Question 1

Define Crystalline

Answer 1

On solidification atoms or ions in crystalline materials arrange themselves in a periodic and regular repeating three-dimensional pattern

Question 2

Define non-Crystalline

Answer 2

These are materials in which long-range order of atom is absent

Question 3

Give examples of crystalline and non-crystalline materials

Answer 3

•All metals, many ceramics and certain polymers form crystalline structures on solidification.
Many polymers have non-crystalline structure, another example is glass

Question 4

Define amorphous

Answer 4

non-crystalline

Question 5

Define Unit Cell

Answer 5

The smallest repetitive volume in a crystalline structure

Question 6

Name the three simple crystal structures

Answer 6

FCC - Face Centered Cubic
BCC - Body Centered Cubic
HCP - Hexagonal Closed Pack

Question 7

Give the details of the FCC arrangement

Answer 7

4 atoms,
coordination # 12
Atomic packing factor 0.74
a=2root2r

Question 8

Give the details of the BCC arrangement

Answer 8

2 atoms
coordination # 8
Atomic packing factor 0.68
a=4r/root3

Question 9

Give the details of the HCP

Answer 9

6 atoms
coordination # 12
Atomic packing factor 0.74

Question 10

Define coordination number

Answer 10

The number of nearest touching atoms

Question 11

Define atomic packing factor

Answer 11

APF = Volume of atoms/Unit cell volume

Question 12

Define Theoretical Density

Answer 12

D=nA/VN
D is density
n is number of atoms
A is atomic mass
V is volume of unit cell
N is Avogadro's number

Question 13

Define polymorphism

Answer 13

The ability of a material to exist in more than one atomic structure

Question 14

Define allotrophy

Answer 14

Polymorphism in elemental materials

Question 15

Define and identify lattice parameters

Answer 15

units that define a unity cell
a, b, c are side lengths
alpha, beta, gamma are inter-axial angles

Question 16

Define crystal system

Answer 16

Unique unit cell shapes, that contain families of atomic arrangements.