Electronic Structure and Periodicity


137. (Solar cells, band gap energy; Ch. 8 "Companion") Two solar cells are to be used by stacking one atop the other. Solar cell A has a band gap energy of 2 eV; solar cell B's band gap energy is 1 eV. Either alone will absorb all the light above its band gap energy. But which one must be on top (nearest the sun) for both to function simultaneously?

A, B


138. (Band gap energy, Ch. 7 "Companion") Given the fact that table salt, NaCl, is a poor conductor of electricity and transparent, where does its band gap energy approximately fall?

in the UV region at > 3 eV, in the visible between 1.7 and 3 eV,
in the IR at < 3 eV


141. (Spectroscopy) Given the three energy levels below, how many emissive transitions are there?

1, 2, 3

A plot of these three emission bands is shown below. Which of the three peaks corresponds to the transition from E3 to E1?

1, 2, 3


144. (Concentration, moles) Demonstration: A mass of 0.02 moles of copper sulfate is to be dissolved in 200 mL of water to make solution A. A mass of 0.04 moles of copper sulfate is to be dissolved in 400 mL of water to make solution B. Will the two solutions have the same concentration?

yes, no

Will they have the same intensity of color in a given pathlength?

yes, no


152. (Polarization) Demonstration: Shine several light sources including a flashlight, LED and pocket laser through a polarizer and observe the transmitted intensity as the polarizer is rotated. Identify whether each source is or is not polarized.


192. Shown below are the emission spectra for two LED's, GaP0.65As0.35 and GaP0.40As0.60. For each LED the spectrum was taken at room temperature and at liquid nitrogen temperature. These four spectra are labeled A through D. Which spectrum corresponds to GaP0.65As0.35 at liquid nitrogen temperature?


A, B, C, D


213. Which of the following extended solids is not isoelectronic with the others?

Sn
InSb
CdTe
InTe


218. Although pure diamonds are colorless, some diamonds have color because of dopants. The Hope Diamond, for example, is blue due to nitrogen (N) dopants. Based on its position in the periodic table, N in diamond acts as a(n):

donor, acceptor

Complete the equilibrium reaction shown below for this dopant:

 

The charge on the product ion is:

positive, negative

The ionization of N leads to the production of a(n):

electron, hole

Which arrow shown below represents the electronic transition corresponding to the ionization of N?

 

A, B

According to LeChatelier's Principle, adding boron (an acceptor) to N-doped diamond will shift the equilibrium of equation 1 toward the:

products, reactants

(A similar set of questions could be asked about doping with B, which can produce yellow diamonds, such as the Smithsonian Canary Diamond.)




223. Which hydrogen atom transition will emit light with lower frequency?

A, B




224. Which of the following electron diagrams represents a correct ground state?

 


A, B, C


 

233. When intense red light strikes a sample of Cs metal in a photoelectric effect experiment, no electrons are ejected from the surface. In contrast, exciting the sample with weak blue light ejects electrons, whose kinetic energy can be measured.

These results are consistent with which of the following conclusions?

Red photons have more energy than blue photons.

Red photons have less energy than blue photons.

Red photons have the same energy as blue photons.

 

A plot of the kinetic energy of the ejected electron vs. incident photon frequency, , would look like

 

A.

B.

An equation describing this experiment is


235. (Nuclear chemistry, periodic properties) Researchers are trying to prepare element 114 (Science, 24 October 1997, 278, 571-572.). If a compound could be made from only this element and hydrogen, based on its position in the periodic table, how many H atoms would you expect to bond to element 114?

 

1, 3, 4, 5


239. Consider two LEDs, one red and one green, both emitting at their band gap energy. Which operating LED can cause a photovoltage in the other LED?

 

The red LED causes photovoltage in the green LED

The green LED causes photovoltage in the red LED


 

 




More questions are needed for this section. Please submit contributions to concept@chem.wisc.edu..