Chapter 12

What is graphene? Why is graphene unique?

Explain the basic principles involved in X-ray crystallography. Include Bragg's law in your explanation.

What is a crystalline lattice? How is the lattice represented with the unit cell?

Make a drawing of each unit cell: simple cubic, body-centered cubic, and face- centered cubic.

What is the difference between hexagonal closest packing and cubic closest packing? What are the unit cells for each of these structures?

What are the three basic types of solids and the composite units of each? What types of forces hold each type of solid together?

What are the three categories of atomic solids?

What kinds of forces hold each of the three basic categories of atomic solids together?

In an ionic compound, how are the relative sizes of the cation and anion related to the coordination number of the crystal structure?

Show how the cesium chloride, sodium chloride, and zinc blende unit cells each contain a cation-to-anion ratio of 1:1.

Show how the fluorite structure accommodates a cation-to-anion ratio of 1:2.

Name and describe the different allotropes of carbon.

What are silicates? What is quartz?

What is the definition of a ceramic? What are the three categories of ceramics?

Describe the difference between vitreous silica and soda-lime glass. What are some advantages and disadvantages of each of these types of glass?

In band theory of bonding for solids, what is a band? What is the difference between the valence band and the conduction band?

In band theory of bonding for solids, what is a band gap? Howdoes the band gap differ in metals, semiconductors, and insulators?

Explain how doping can increase the conductivity of a semiconductor. What is the difference between an n-type semiconductor and a p-type semiconductor?

What is the trend in the size of the band gap as you move down the column of the group 4A elements?

What is a polymer? What is the difference between a polymer and a copolymer?

How do an addition polymer and a condensation polymer differ from each other?

An X-ray beam with l = 154 pm incident on the surface of a crystal produced a maximum reflection at an angle of u = 28.3 . Assuming n = 1, calculate the separation between layers of atoms in the crystal.

An X-ray beam of unknown wavelength is diffracted from a NaCl surface. If the interplanar distance in the crystal is 286 pm and the angle of maximum reflection is found to be 7.23 , what is the wavelength of the X-ray beam? (Assume n = 1.)

Determine the number of atoms per unit cell for each metal. a. Polonium b. Tungsten c. Nickel

Calculate the packing efficiency of the body-centered cubic unit cell. Show your work.

Calculate the packing efficiency of the face-centered cubic unit cell. Show your work.

Polonium crystallizes with a simple cubic structure. It has a density of 9.3 g/cm3, a radius of 167 pm, and a molar mass of 209 g/mol. Use these data to calculate Avogadro's number (the number of atoms in one mole).

Palladium crystallizes with a face-centered cubic structure. It has a density of 12.0 g/cm3, a radius of 138 pm, and a molar mass of 106.42 g/mol. Use these data to calculate Avogadro's number.

Identify each solid as molecular, ionic, or atomic. a. Ar(s) b. H2O(s) c. K2O(s) d. Fe(s)

Identify each solid as molecular, ionic, or atomic. a. CaCl2(s) b. CO2(s) c. Ni(s) d. I2(s)

Which solid in each pair has the higher melting point and why? a. TiO2(s) or HOOH(s) b. CCl4(s) or SiCl4(s) c. Kr(s) or Xe(s) d. NaCl(s) or CaO(s)

Which solid in each pair has the higher melting point and why? a. Fe(s) or CCl4(s) b. KCl(s) or HCl(s) c. Ti(s) or Ne(s) d. H2O(s) or H2S(s)

Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic. a. B4C b. Mg2SiO4 c. MoSi2

Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic. a. TiB2 b. ZrO2 c. NaAlSi3O8

What are the name and formula of the compound commonly used in the manufacture of glass to reduce its tendency to crack or shatter under thermal shock?

One of the key components in the manufacture of Portland cement is Ca3SiO5, a compound that is obtained by firing the reactants in a kiln at 1400-1500 C. Assign an oxidation state to each element in this compound.

Replacement of aluminum ions in kaolinite with magnesium ions yields a compound with the formula Mg3Si2O5(OH)4. Assign an oxidation state to each element in this compound.

Which solid would you expect to have little or no band gap? a. Zn(s) b. Si(s) c. As(s)

Which solid would you expect to have the largest band gap? a. As(s) b. Sb(s) c. Bi(s)

A substance has a band gap of 6.9 eV at 273 K. Is this substance best classified as an insulator, a semiconductor, or a metal?

A substance has a band gap of 0.85 eV at 273 K. Is this substance best classified as an insulator, a semiconductor, or a metal?

Indicate if each solid forms an n-type or a p-type semiconductor. a. germanium doped with gallium b. silicon doped with arsenic

Indicate if each solid forms an n-type or a p-type semiconductor. a. silicon doped with gallium b. germanium doped with antimony

Which wavelength of light (in nm) is emitted if an electron moves from the conduction band to the valence band in a sample of diamond (diamond has a band gap of 5.5 eV)?

One kind of polyester is a condensation copolymer formed from terephthalic acid and ethylene glycol. Draw the structure of the dimer. [Hint: Water (circled) is eliminated when the bond between the monomers forms.]

Nomex, a condensation copolymer used by firefighters because of its flame- resistant properties, forms from isophthalic acid and m-aminoaniline. Draw the structure of the dimer. (Hint:Water is eliminated when the bond between the monomers forms.)

Consider the face-centered cubic structure shown here: a. What is the length of the line (labeled c) that runs diagonally across one of the faces of the cube in terms of r (the atomic radius)? b. Use the answer to part a and the Pythagorean theorem to derive the expression for the edge length (l) in terms of r.

Consider the body-centered cubic structure shown here: a. What is the length of the line (labeled c) that runs from one corner of the cube diagonally through the center of the cube to the other corner in terms of r (the atomic radius)? b. Use the Pythagorean theorem to derive an expression for the length of the line (labeled b) that runs diagonally across one of the faces of the cube in terms of the edge length (l). c. Use the answer to parts a and b along with the Pythagorean theorem to derive the expression for the edge length (l) in terms of r.

The volume of a unit cell of diamond is 0.0454 nm3, and the density of diamond is 3.52 g/cm3. Find the number of carbon atoms in a unit cell of diamond.

The density of an unknown metal is 12.3 g>cm3, and its atomic radius is 0.134 nm. It has a face-centered cubic lattice. Find the atomic mass of this metal.