The Structure of Crystalline Solids

Question 1

illustrating how the spots (i.e., the diffraction pattern) in (a) are produced

Answer 1

schematic diagram

Question 2

a light-weight
automobile wheel that is
made of magnesium

Answer 2

mag wheel

Question 3

___ material is one in which the atoms are situated in a repeating or
periodic array over large atomic distances—that is, long-range order exists, such
that upon solidification, the atoms will position themselves in a repetitive three-
dimensional pattern, in which each atom is bonded to its nearest neighbour atoms.

Answer 3

crystalline

Question 4

of the material, the manner in which atoms, ions, or
molecules are spatially arranged.

Answer 4

crystal structure

Question 5

constituent particles are arranged in a regular fashion containing short range as well as long range order

Answer 5

crystalline solids

Question 6

crystalline particles are NOT arranged in any regular fashion; they may be at the most some range order

Answer 6

amorphous solids

Question 7

All metals
Most Ceramics
Some polymers

Answer 7

crystalline solids

Question 8

Rubber
Glass
Plastics
Polymers

Answer 8

amorphous solids

Question 9

___ is used in the context of crystal structures; in this sense ___ means a
three-dimensional array of points coinciding with atom positions (or sphere centres)

Answer 9

lattice

Question 10

small repeat entities

Answer 10

unit cells

Question 11

Three relatively simple crystal structures are found
for most of the common metals

Answer 11

•face-centered cubic (FCC) crystal structure

•body centered cubic (BCC) crystal structure

•hexagonal close-packed (HCP) crystal structure

Question 12

It contains 4 atoms in a unit cell. The atomic packing factor for ___ is
0.74 which means it has 26% void space per unit cell.

Answer 12

FCC

Question 13

a = 2R√2

where:

a = atomic lenght weight
R = atomic radius

Answer 13

FCC

Question 14

Two other important characteristics of a crystal structure

Answer 14

Coordination number
Atomic packing factor (APF)

Question 15

For metals, each atom has the
same number of nearest-neighbour or touching atoms

Answer 15

Coordination number

Question 16

is the sum of the sphere
volumes of all atoms within a unit cell (assuming the atomic
hard-sphere model) divided by the unit cell volume

Answer 16

Atomic packing factor (APF)

Question 17

common metallic crystal structure also has a cubic unit cell with atoms
located at all eight corners and a single atom at the cube center.

Answer 17

Body-Centered Cubic (BCC) Crystal Structure

Question 18

The atomic packing factor for BCC is 0.68 which means it has 32%
void space per unit cell. Contain 2 atoms in a unit cell

Answer 18

Body-Centered Cubic (BCC) Crystal Structur

Question 19

The equivalent of 6 atoms is contained in each unit cell; one-sixth of each
of the 12 top and bottom face corner atoms, one-half of each of the 2
center face atoms, and all 3 midplane interior atoms. The atomic packing
factor for HCP is 0.74 which means it has 26% void space per unit cell.

Answer 19

Hexagonal Close-Packed (HCP) Crystal Structure

Question 20

Not all metals have unit cells with cubic symmetry;
the final common metallic crystal structure has a unit
cell that is hexagonal

Answer 20

Hexagonal Close-Packed (HCP) Crystal Structure