Chapter 3 onward

Question 1

How does density typically compare among metals, ceramics, and polymers?

Answer 1

Metals > Ceramics > Polymers
Reasons:

Metals have close-packing and large atomic masses.
Ceramics have less dense packing and lighter elements.
Polymers have low packing density and lighter elements like C, H, O.

Question 2

Why do metals typically have higher densities than ceramics and polymers?

Answer 2

Metals have close-packed structures (metallic bonding).
Often contain heavier elements.

Question 3

What are the typical crystal structures for metals?

Answer 3

Common metallic crystal structures:

FCC (Face-Centered Cubic)
BCC (Body-Centered Cubic)
HCP (Hexagonal Close-Packed)

Question 4

What is the coordination number and atomic packing factor for FCC and HCP structures?

Answer 4

Both FCC and HCP have:

Coordination number: 12
Atomic packing factor: 0.74

Question 5

What are single crystals and polycrystals?

Answer 5

Single Crystals: Properties vary with direction (anisotropic).
Polycrystals: May be isotropic (random grain orientation) or anisotropic (textured grains).

Question 6

What is polymorphism?

Answer 6

Polymorphism refers to the existence of two or more distinct crystal structures for the same material.
Examples:

Carbon: diamond, graphite
Iron: α-Fe, γ-Fe, δ-Fe

Question 7

What is the function of X-ray diffraction in materials science?

Answer 7

X-ray diffraction is used to determine crystal structure and interplanar spacing.

Question 8

What factors influence material density?

Answer 8

Material density depends on:

Atomic weight of elements
Atomic packing in the crystal structure
Crystal geometry (e.g., FCC, BCC, HCP)

Question 9

Measurement of
critical angle, θ c,
allows computation of
, __?

Answer 9

D, planar spacing

Question 10

What is defraction

Answer 10

elastic scattering of atoms

Question 11

We can predict the_____ of a material, provided we
know the atomic weight, atomic radius, and crystal
geometry

Answer 11

density

Question 12

What is anisotropic

Answer 12

Anisotropic materials show different properties in different directions.

Question 13

What is an isotropic material?

Answer 13

common term in materials science that means uniform in all directions. Isotropic materials exhibit the same material properties in all directions. Metals and glasses tend to be isotropic.

Question 14

Single crystals are generally _____

Answer 14

anisotropic

Question 15

polycrystals are generally _____

Answer 15

Isotropic

Question 16

Give 2 statements that satisfy the Pauli exclusion principle.

Answer 16

Electron state can hold no more than two electrons.
Electrons with the same state must have opposite spins.