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Problem 60
Which solid would you expect to have the largest band gap? a. As(s) b. Sb(s) c. Bi(s)
Problem 61
How many molecular orbitals are present in the conduction band of a lithium crystal with a mass of 11.2 g?
Problem 63
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?
Problem 66b
Indicate if each solid forms an n-type or a p-type semiconductor.
a. silicon doped with gallium
b. germanium doped with antimony
Problem 67
Does a photon of red light with a frequency of 4.29⨉1014 Hz have sufficient energy to promote an electron from the valence band to the conduction band in a sample of silicon (the band gap in silicon is 1.11 eV)?
- What is the wavelength of light (in nm) emitted when an electron moves from the conduction band to the valence band in a sample of diamond, which has a band gap of 5.5 eV?
Problem 68
Problem 69
Teflon is an addition polymer formed from the monomer shown here. Draw the structure of the polymer.
Problem 70
Saran, the polymer used to make saran wrap, is an addition polymer formed from two monomers—vinylidene chloride and vinyl chloride. Draw the structure of the polymer. (Hint: The monomers alternate.)
Problem 74
Polyacrylonitrile (PAN) is an addition polymer with the struc- ture shown here. Draw the structure of the monomer.
Problem 78
Copper iodide crystallizes in the zinc blende structure. The sep- aration between nearest neighbor cations and anions is approximately 311 pm, and the melting point is 606 °C. Potassium chloride, by contrast, crystallizes in the rock salt structure. Even though the separation between nearest-neighbor cations and anions is greater (319 pm), the melting point of potassium chlo- ride is higher (776 °C). Explain.
- 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.
Problem 81
Problem 82
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
Problem 83
An unknown metal is found to have a density of 7.8748 g/cm3 and to crystallize in a body-centered cubic lattice. The edge of the unit cell is 0.28664 nm. Calculate the atomic mass of the metal.
- When spheres of radius r are packed in a body-centered cubic arrangement, they occupy 68.0% of the available volume. Use the fraction of occupied volume to calculate the value of a, the length of the edge of the cube, in terms of r.
Problem 84
Problem 86
Calculate the fraction of empty space in cubic closest packing to five significant figures.
- What is a tetrahedral site in a closest-packed lattice formed by?
Problem 87
Problem 88
X-ray diffractometers often use metals that have had their core electrons excited as a source of X-rays. Consider the 2p → 1s transition for copper, which is called the K⍺ transition. Calculate the wavelength of X-rays (in Å) given off by the K⍺ transition if the energy given off by a mole of copper atoms is 7.77⨉105 kJ.(1Å = 10-10 m)
- Why is it necessary to use the Kα transition (2p → 1s) in copper (see Problem 88) to generate X-rays? Why not use, for example, the 4s → 3p transition?
Problem 89