Chapter 3: Structure of Crystalline Solids

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Which of the following materials typically exhibit long-range periodic packing of atoms?

Liquids and gases

All glasses and some polymers

Most metals and many ceramics (correct)

Noncrystalline solids and amorphous materials

Which of the following is an example of a single crystal material?

Window glass

Polyethylene plastic

Diamond abrasives (correct)

Concrete

What is the primary difference in atomic packing between crystalline and amorphous materials?

Crystalline materials have shorter bond lengths between neighbors.

Amorphous materials have stronger neighbor bond energies.

Crystalline materials have higher energy and lower density.

Amorphous materials have random packing, while crystalline materials have ordered packing. (correct)

Which of the following statements about neighbor bond lengths and energies in crystalline and amorphous materials is correct?

Crystalline materials have shorter bond lengths and higher bond energies. Signup and view all the answers

Which statement is true about the energy and packing of crystalline materials compared to amorphous materials?

Crystalline materials have lower energy and higher density. Signup and view all the answers

What is the primary advantage of single crystal materials like turbine blades?

Higher strength and durability Signup and view all the answers

What is the primary characteristic of a polycrystalline material?

It contains many individual grains or small crystals Signup and view all the answers

Which of the following statements about the unit cell in a crystal lattice is NOT true?

Opposite faces (or edges) are always parallel Signup and view all the answers

In the hard-sphere model for crystal structures, what does it mean for atoms to "touch" their nearest neighbors?

The atoms are at their minimum possible distance apart Signup and view all the answers

What is the coordination number of an atom in a crystal structure?

The number of nearest (or touching) neighboring atoms Signup and view all the answers

Which of the following is NOT one of the seven crystal systems?

Hexagonal Signup and view all the answers

In the context of crystal structures, what is the purpose of the hard-sphere model?

To provide a simplified representation of atom arrangements in crystals Signup and view all the answers

What is the coordination number for a simple cubic (SC) structure?

6 Signup and view all the answers

What is the atomic packing factor (APF) for a simple cubic structure?

0.52 Signup and view all the answers

What is the number of atoms per unit cell in a simple cubic structure?

1 Signup and view all the answers

In which direction do the atoms touch each other in a body-centered cubic (BCC) structure?

Along the cube diagonals Signup and view all the answers

Which crystal system has a 6-fold axis of rotation?

Hexagonal (Trigonal) Signup and view all the answers

If the radius of an atom in a simple cubic structure is R, what is the edge length a of the unit cell in terms of R?

$a = 2R$ Signup and view all the answers

What is the relationship between the densities of different material classes?

The density of metals is greater than the density of ceramics, which is greater than the density of polymers. Signup and view all the answers

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

Metals have close-packed structures and metallic bonding, leading to higher densities. Signup and view all the answers

What is the main reason ceramics typically have lower densities than metals?

Ceramics have less dense packing and often contain lighter elements. Signup and view all the answers

What is the relationship between the packing density and the density of different material classes?

Materials with higher packing density have higher densities, and vice versa. Signup and view all the answers

Why do polymers typically have the lowest densities among the material classes?

Polymers have low packing density and often contain lighter elements like C, H, and O. Signup and view all the answers

Which of the following statements about the densities of different material classes is NOT supported by the information provided in the text?

The density of a material is determined solely by its atomic composition and packing. Signup and view all the answers

What is the coordination number (CN) for a body-centered cubic (BCC) structure?

8 Signup and view all the answers

What is the atomic packing factor (APF) for a face-centered cubic (FCC) structure?

0.74 Signup and view all the answers

How many atoms are present on average in a unit cell of a body-centered cubic (BCC) structure?

2 Signup and view all the answers

What is the relationship between the atomic radius (R) and the lattice parameter (a) for a body-centered cubic (BCC) structure?

$R = a/\sqrt{3}$ Signup and view all the answers

How many atoms are present on average in a unit cell of a face-centered cubic (FCC) structure?

4 Signup and view all the answers

What is the relationship between the atomic radius (R) and the lattice parameter (a) for a face-centered cubic (FCC) structure?

$R = a/\sqrt{2}$ Signup and view all the answers