test2b - 3.091 Fall Term 2004 Test #23 page 2 Problem #1...

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Unformatted text preview: 3.091 Fall Term 2004 Test #23 page 2 Problem #1 (20%) (a) Estimate the value of the screening factor in Moseley’s Law associated with the Ma line. Show your reasoning. (8%)—-%( finer/Mada J7 e’fim‘fiw m I7=4 —>q=3 ,t “flax. Ila. pécfi’w %¢M 3 76 WW)? 7“? W fi=¢, ,r 2 (fly ‘4 8(hzz) +/6fl4=3 ) -: 2:; «W MW / 76 W racmc7m fli—CM (7’ g 27 ’Voc (b) You suspect that aluminum you purchased from a recycling facility has been contaminated with a heavy metal. The x—ray emission spectrum of your metal reveals the presence of a Km line at x = 1.85 x 10—11 m. What is the impurity? m We 2 W = 2/4 aKZfi); J. A z. '4' L: 2" "7m ( ) 2, "~73": 5x7? —— .n—n —-—- (a): K 61' wo"”¢ /- Hm”) [’2' = 6L =9) 75 '7’ 3.09] Fall Term 2004 Test #23 page 3 Problem #2 (24 %) (a) Using proper crystallographic notation, identify the direction and the plane depicted in the above sketches. (8%) (b) The figure below shows the unit cell of the compound AxBy. The dark spheres represent atoms of B. (i) Name the Bravais lattice of AxBy. Q: (4%) (ii) Identify the basis of the crystal structure of AXBy. (4%) l4 33 (iii) Determine the chemical formula of AxBy. Show your reasoning. 3.09] Fall Term 2004 Test #23 page 4 Problem #3 (24%) ' (a) The figure below shows the temperature dependence of charge carrier density in germanium (Ge) doped with boron (B). Explain the dominant process associated with the generation of charge carriers (i) in region 1 and (ii) in region 2. 0 Guam flaw; 171W 3; 4 #791103: CW1 @ 179%! 75'“ charge 76 denSity region2 @ _-:> Mil/véfw region 1 temperature d M 6. (12%) (b) The concentration of dopant can be on the order of 1017/cm3, yet the energy of all these impurities is represented by a single level as opposed to a band. Explain why this is not a violation of the Pauli Exclusion Principle. (6%) WJMGL fiyldzfi‘fi/ any flaw $6447— Wm at 4 WW5 a Wan/Z? 144W 5%wa (c) Explain the trend in the value of the wavelength of the absorption edge in the following homologous series: CdS, CdSe, CdTe. W W W I‘M/MW MW -'- Mtwflt g I W § {2 /\aé§ a? 7 (6%) 3.091 Fall Term 2004 Test #23 page 5 Problem #4 (32 %) (a) Draw a 3—dimensional representation of the molecular geometry around the central atom (not simply the Lewis structure) of IClF4. . J W ) ,m‘ mwm/amte W , . -~ 65b F cc '1134 if #5. 5'3 F ' F .1. fF-“x 4 Hi“ I #8 I F ‘ H ‘w‘; .. F ¥_""—\ F (b) Name the type of hybrid orbitals that the central atom forms. 3 Z (2%) S’ d (c) Is the molecule pol or nonpolar? Justify. W (8% (d) For each pair of compounds, identify the one with the higher boiling point. Justify your choice. (i)SnCl4 IT lion W Wag/A Wearth (18%) nggCé r‘r flMu-z civM—UC’W‘Q ’Ve’”‘””‘°’ Wdffla~a>fcmufdmdle film 716Mer 1 (ii) HBr an «@ #6} if Caz/Mf‘ .; $M- /W/QO7§W War/Me ‘ ("8,- IT fwu‘c, ._.. (nd Cus v/sz Mac 42/7’! W @790» 02,9: S“.- ch Vat/Ma M aZPI‘C/imflw .; Q—o Mal/va 22% ‘ «fl Wwww W ...
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test2b - 3.091 Fall Term 2004 Test #23 page 2 Problem #1...

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