Chapter 12: Problem 70
Which of the following properties are typical characteristics of a covalent- network solid, a metallic solid, or both: (a) ductility, (b) hardness, (c) high melting point?
Chapter 12: Problem 70
Which of the following properties are typical characteristics of a covalent- network solid, a metallic solid, or both: (a) ductility, (b) hardness, (c) high melting point?
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Get started for freeIndicate whether each statement is true or false: $$ \begin{array}{l}{\text { (a) Elastomers are rubbery solids. }} \\ {\text { (b) Thermosets cannot be reshaped. }} \\ {\text { (c) Thermoplastic polymers can be recycled. }}\end{array} $$
Cadmium telluride is an important material for solar cells. (a) What is the band gap of CdTe? (b) What wavelength of light would a photon of this energy correspond to? (c) Draw a vertical line at this wavelength in the figure shown in Exercise \(12.75,\) which shows the light output of the sun as a function of wavelength. (d) With respect to silicon, does CdTe absorb a larger or smaller portion of the solar spectrum?
Sodium oxide \(\left(\mathrm{Na}_{2} \mathrm{O}\right)\) adopts a cubic structure with Na atoms represented by green spheres and O atoms by red spheres. $$ \begin{array}{l}{\text { (a) How many atoms of each type are there in the unit cell? }} \\ {\text { (b) Determine the coordination number and describe the }} \\ {\text { shape of the coordination environment for the sodium }} \\\ {\text { ion. }} \\ {\text { (c) The unit cell edge length is } 5.550 \text { A. Determine the den- }} \\ {\text { sity of } \mathrm{Na}_{2} \text { O. }}\end{array} $$
Indicate whether each statement is true or false: $$ \begin{array}{l}{\text { (a) The band gap of a semiconductor decreases as the parti- }} \\ {\text { cle size decreases in the } 1-10 \text { -nm range. }} \\\ {\text { (b) The light that is emitted from a semiconductor, upon }} \\\ {\text { external stimulation, becomes longer in wavelength as }} \\ {\text { the particle size of the semiconductor decreases. }}\end{array} $$
When you shine light of band gap energy or higher on a semiconductor and promote electrons from the valence band to the conduction band, do you expect the conductivity of the semiconductor to (a) remain unchanged, (b) increase, or (c) decrease?
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