Lattice Structures in Solids

Chm 115 Final Exam

Simple Cubic, Body-Centered Cubic, And Face-Centered Cubic

The three cubic cells, which are unit cells, that we will focus on are:

Coordinate Numbers (C.N.)

The number of nearest neighboring atoms that surround it (number of atoms it touches).

a = 2r

What is the relationship of length of cubic cell (a) to radius of atom ® for simple cubic?

a = 4r/sqrt(3)

What is the relationship of length of cubic cell (a) to radius of atom ® for body-centered cubic?

a = 4r/sqrt(2)

What is the relationship of length of cubic cell (a) to radius of atom ® for face-centered cubic?

52%

How much of the simple cubic volume is occupied?

68%

How much of the body-centered cubic volume is occupied?

74%

How much of the face-centered cubic volume is occupied?

6

What is the coordinate number of simple cubic?

8

What is the coordinate number of body-centered cubic?

12

What is the coordinate number of face-centered cubic

1/8 And ¼ And ½ And 1

The atom (or ion) count per unit cell depends on their position at corner ___, edge ____, face ____, or interior __.

Packing Efficiency Or Void Space

Use a-to-r ratio to determine:

Unit-cell Density (g/cm³)

Use molar mass of atom (g/mol) to calculate:

pm or Picometer or 1×10^-12 meters

What is the units of a?