Chp. 3 Summary

Question 1

Atoms in crystalline solids are positioned in

Answer 1

orderly, repeated patterns. For nincrystaline or amorphous materials they are randon and disordered

Question 2

Crystal structures are specified in terms of

Answer 2

parallelepiped unit cells, which are

characterized by geometry and atom positions within.

Question 3

The concept of crystal system is used to

Answer 3

classify crystal structures on the basis of

unit cell geometry. (unit cell edge lengths and interaxial angles)

Question 4

Name 7 Crustal systems

Answer 4

cubic, tetragonal, hexagonal, orthorhombic, rhombohedral

(trigonal), monoclinic, and triclinic.

Question 5

Crystallographic points in a unit cell is specified using

Answer 5

coordinates that

are fractional multiples of the cell edge lengths.

Question 6

Directional indices are computed in terms of

Answer 6

the vector projection on each

of the coordinate axes.

Question 7

Planar (or Miller) indices are determined from

Answer 7

from the reciprocals of axial intercepts.

Question 8

What are Single Crystals?

Answer 8

materials in which the atomic order extends uninterrupted over
the entirety of the specimen

Question 9

Define polycryistalline

Answer 9

Solid being composed

of many small crystals or grains having different crystallographic orientations.

Question 10

Define anisotropy

Answer 10

the directionality dependence of properties. For isotropic materials,
properties are independent of the direction of measurement.

Question 11

Noncrystalline solids

Answer 11

lack a systematic and regular arrangement of atoms

or ions over relatively large distances (on an atomic scale)