1. The difference between an ionic bond and a covalent bond is Q42.1 1. ionic bonds are only found in crystals such as sodium chloride (NaCl) where there are many atoms in close proximity 2. covalent bonds are only found in molecules with three or more atoms 3. ionic bonds are highly directional, while covalent bonds are not 4. ionic bonds involve the transfer of an electron from one atom to another, while covalent bonds involve electrons that spend much of their time between atoms

2. The difference between an ionic bond and a covalent bond is A42.1 1. ionic bonds are only found in crystals such as sodium chloride (NaCl) where there are many atoms in close proximity 2. covalent bonds are only found in molecules with three or more atoms 3. ionic bonds are highly directional, while covalent bonds are not 4. ionic bonds involve the transfer of an electron from one atom to another, while covalent bonds involve electrons that spend much of their time between atoms

3. When a diatomic molecule rotates very rapidly, the atoms that comprise the molecule move slightly farther apart (the molecule “stretches”). What effect does this have on the rotational energy levels of the molecule? Q42.2 1. the effect is on the low-energy levels, which are spaced closer together than if the molecule did not stretch 2. the effect is on the low-energy levels, which are spaced farther apart than if the molecule did not stretch 3. the effect is on the high-energy levels, which are spaced closer together than if the molecule did not stretch 4. the effect is on the high-energy levels, which are spaced farther apart than if the molecule did not stretch

4. When a diatomic molecule rotates very rapidly, the atoms that comprise the molecule move slightly farther apart (the molecule “stretches”). What effect does this have on the rotational energy levels of the molecule? A42.2 1. the effect is on the low-energy levels, which are spaced closer together than if the molecule did not stretch 2. the effect is on the low-energy levels, which are spaced farther apart than if the molecule did not stretch 3. the effect is on the high-energy levels, which are spaced closer together than if the molecule did not stretch 4. the effect is on the high-energy levels, which are spaced farther apart than if the molecule did not stretch

5. At absolute zero (T = 0 K), what is the difference between a semiconductor and an insulator? Q42.3 1. the conduction band is empty in a semiconductor but partially filled in an insulator 2. the conduction band is partially filled in a semiconductor but empty in an insulator 3. the energy gap between the valence and conduction bands is large in a semiconductor but small in an insulator 4. the energy gap between the valence and conduction bands is small in a semiconductor but large in an insulator

6. At absolute zero (T = 0 K), what is the difference between a semiconductor and an insulator? A42.3 1. the conduction band is empty in a semiconductor but partially filled in an insulator 2. the conduction band is partially filled in a semiconductor but empty in an insulator 3. the energy gap between the valence and conduction bands is large in a semiconductor but small in an insulator 4. the energy gap between the valence and conduction bands is small in a semiconductor but large in an insulator

7. If you increase the temperature of a block of copper from 300 K to 600 K, what happens to the average kinetic energy of the electrons in the conduction band? (Copper remains a solid at these temperatures.) Q42.4 1. the average kinetic energy increases by a factor of 4 2. the average kinetic energy increases by a factor of 2 3. the average kinetic energy increases by a factor of 2 1/2 4. the average kinetic energy changes by only a small factor

8. If you increase the temperature of a block of copper from 300 K to 600 K, what happens to the average kinetic energy of the electrons in the conduction band? (Copper remains a solid at these temperatures.) A42.4 1. the average kinetic energy increases by a factor of 4 2. the average kinetic energy increases by a factor of 2 3. the average kinetic energy increases by a factor of 2 1/2 4. the average kinetic energy changes by only a small factor

9. How would you expect the electric conductivity of a semiconductor to vary with increasing temperature? Q42.5 1. it should increase, because more electrons are thermally excited from the valence band into the conduction band 2. it should increase, because more electrons are removed from their parent atoms and added to the valence band 3. it should decrease, because the added thermal energy breaks apart correlated electron pairs 4. it should decrease, because the atoms in the crystal will vibrate more and thus block the flow of electrons

10. How would you expect the electric conductivity of a semiconductor to vary with increasing temperature? A42.5 1. it should increase, because more electrons are thermally excited from the valence band into the conduction band 2. it should increase, because more electrons are removed from their parent atoms and added to the valence band 3. it should decrease, because the added thermal energy breaks apart correlated electron pairs 4. it should decrease, because the atoms in the crystal will vibrate more and thus block the flow of electrons