SolidStateKEYF11-1

SolidStateKEYF11-1 - Chem124 Fall2011 Complete KEY to Solid...

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Chem 124 Fall 2011 Dr. Neff Complete KEY to Solid State Chemistry Workbook You should be able to work any problem shown here for Quiz 3 1. Find the repeating square unit cells in each of the following patterns.
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Chem 124 Fall 2011 Dr. Neff 2. 2. In each of the cases shown below, draw z-diagrams for the unit cells shown and determine the net number of atoms per unit cell. a) Nickel, as well as many other metals, crystallizes in the structure shown below 4 net atoms, from 8 x 1/8 + 6 x 1/2 b) Polonium is the only element known to crystallize in the structure shown below. 1 net atoms, from 8 x 1/8 c) Iron, as well as many other metals, crystallizes in the structure shown below 2 net atoms, from 8 x 1/8 + 1 d. Shown in the figure below is the unit cell structure for one form of C, the diamond structure. Also shown is the corresponding z-diagram for this unit cell. Using this z-diagram, determine the contribution of atoms to each z-layer, and from this, determine the net number of atoms contained within one unit cell. z = 0, 1 z = 0.5
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Chem 124 Fall 2011 Dr. Neff In z = 0,1, see a net contribution of 2 atoms In z = 0.25 there are 2 atoms completely in cell In z = 0.5, there are 4 atoms each 1/2 in the cell so 4 x 1/2 = 2 z = 0.75 is just like z = 0.25, so there are 2 atoms completely in cell There are 8 net atoms in this unit cell 3. Find the simplest formula for the following unit cell structure. Put the “elements” in the formula in alphabetical order. z=0, 1 z= 0.25 z = 0.5 z = 0.75 KEY: A 2 atoms in body of unit cell B 4 x 1/8 + 6 x ¼ = 2 C 2 x ½ + 1 = 2 A 2 B 2 C 2 which reduces to ABC 4. a) Draw a set of z-diagrams for a unit cell having the hypothetical formula M 2 N. Be sure that the unit cell is a cubic variant and has a regular structure. Remember that the bottom (z = 0) and top (z = 1) layers must be the same. Note that there is probably more than one way to draw z-diagrams to represent such a structure. One possible way to answer this: M = N = z=0, 1 z= 0.5 Two more ways Key M N z = 0,1 z = 0.5 This one is a bcc arrangement of M atoms or
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Chem 124 Fall 2011 Dr. Neff z = 0 ,1 z = 0.25 z = 0.5 z = 0.75 This is fcc arrangement of M atoms b) Give the chemical formula for an ionic salt that might have the formula in the previous problem. Use the periodic table to help you. (M is a metal, N a nonmetal.) Then name this compound using standard chemical nomenclature rules. The simplest way to get such a formula would be with a metal with a +1 charge and a nonmetal with a –2 charge, so sodium (Na) and sulfur (S) would work, Na 2 S, sodium sulfide. Sodium oxide would also work. Na 2 O. DO expect to see a density calculation on the QUIZ this week 5. The metallic radius of manganese, 25 Mn, is 127 pm. If it crystallizes in a body-centered cubic unit cell, what is its density in g/cm 3 ? ΒΧΧυνιτχελλχονταινσ2ατομσ
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SolidStateKEYF11-1 - Chem124 Fall2011 Complete KEY to Solid...

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