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This is sections 11.7 and 11.8 in the 10th and 11th editions and <br>
this same material from the 11th edition is on Carmen for those
using<br>
the 12th - 14th editions. Remember, no matter which edition<br>
you're using we are not using chapter 12.<br>
<br>
I covered the primitive(simple), body-centered and face-centered <br>
cubic structures. I gave a lot of info about these (# particles/uc,
<br>
how the particles touch, relationship between edge-length and
radius, <br>
coordination number, % empty space, type of holes the particles <br>
are in, etc.). I also covered close-packing of spheres and we saw <br>
a non-cubic type of packing (Hexagonal close-packing, hcp) and
learned <br>
the cubic-close packed (ccp) structure is the same as a fcc
structure. <br>
All of this discussion was for identical particles in the u.c. (i.e.
same <br>
size, like all Fe atoms, all CO2 molecules, etc.) <br>
<br>
This was all covered in section 11.7 in the 10th and 11th editions <br>
Some of this is summarized in the following link (found at the
"Notes"<br>
link on my web page):<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/notes/unit_cell_table.pdf"><b>Chapter
11/12 - Unit Cell Table for Identical Sized Particles</b></a><br>
<br>
I covered the NaCl structure in detail and a few things about three<br>
other ionic crystal structures.<br>
<br>
In the 10th and 11th editions the structure of NaCl is discussed in
<br>
section 11.7 and CsCl, ZnS and CaF2 are discussed in section 11.8. <br>
For the 12th - 14th editions use what's on Carmen (from the 11th
ed.).<br>
<br>
NaCl is described as a face-centered cubic unit cell. The problem
is<br>
it doesn't look like the fcc unit cell described for a substance in
which<br>
all particles are identical. I explained why it is called a fcc
structure and<br>
how it differs from the fcc unit cell for identical sized particles
in lecture.<br>
For NaCl understand the unit cells and related information given in
class,<br>
notes and the textbook for NaCl. This includes its structure,
placement<br>
of the ions, how anions and cations touch (along an edge),
relationship<br>
between edge length and radii of the ions, number of nearest
neighbors<br>
and what they are, for both the cation and anion, type of "hole"
each ion<br>
"sits" in, unit cell calculations, etc. I don't generally refer to
NaCl as<br>
face-centered but call it the "NaCl structure". So in a problem I
might state<br>
something like "the substance has an NaCl like structure". You
should<br>
know what that means.<br>
<br>
For CsCl, ZnS and CaF2 you should know where the atoms are in the
u.c.<br>
and the number of formula units in a unit cell.<br>
<br>
In doing unit cell calc. for ionic structures you must know how many<br>
formula units there are in a unit cell (e.g. NaCl, ZnS and CaF2 all
have<br>
4 f.u. per unit cell, CsCl has 1 fu/uc). For CsCl, ZnS and CaF2 you
only<br>
need to know the # fu/uc. I've included a link to a table with all
the<br>
information for these 4 ionic structures. You should know what's
listed<br>
for NaCl. For the other 3 ionic crystal structures just know the
placement<br>
of the ions and the #fu/uc. You can find what you need for these
ionic<br>
structures marked in <b><font color="#ff0000">red</font></b> at the
following link (found at the "Notes" link on<br>
my web page):<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/notes/ionic_unit_cell_table_filled.pdf"><b>Chapter
11/12 - Unit Cell Table for Ionic Structures (know stuff in red)</b></a><br>
<br>
Furthermore, I would highly suggest using dimensional analysis to <br>
do unit-cell calculations rather than the way shown in the book. I<br>
did them this way in class and I think in the long run it makes them
<br>
easier. You will find you can do the uc calc. for ionic structures
in the <br>
same way as you do for atoms or molecules if you think in terms of <br>
"formula-units" (f.u.) for the ionic compounds. NaCl is the
"formula unit" <br>
for sodium chloride. You treat it just as if it were a molecule.
For <br>
CO2, which is a fcc structure, you have 4 CO2 molecules per u.c. and
<br>
for NaCl you have 4 NaCl f.u. per u.c. Thus, you can do a density<br>
calculation the same way for CO2 and NaCl as you would for something<br>
like the Ag example I did in class (using the MW for CO2 or the
formula wt. <br>
for NaCl and the number of particles/uc in the same way you would
use <br>
the atomic wt. and # atoms/uc for an atom like Ag). <br>
<br>
For unit cell calculations you should be able determine the
following:<br>
<br>
1) density (g/cm^3)<br>
2) volume (cm^3/uc) - includes edge length and particle radius<br>
3) AW, MW, FW (g/mol)<br>
4) unit cell type (sc, bcc, fcc) - (#particles/uc)<br>
5) Avogadro's Number (#particles/mol)<br>
<br>
I've included the units you're after when doing these problems using<br>
dimensional analysis. This includes calculations for ionic
structures<br>
(particle radius for just NaCl). <br>
<br>
Don't forget about the following web site where you can look at
these <br>
structures in 3-D and rotate them around.<br>
<br>
<a class="moz-txt-link-freetext"
href="http://undergrad-ed.chemistry.ohio-state.edu/xtal/index.html">http://undergrad-ed.chemistry.ohio-state.edu/xtal/index.html</a><br>
<br>
Once there, click on "Crystal Structures" at the bottom. At the top
of<br>
the page which comes up you can load the structures for a single
type<br>
of particle (sc, bcc, fcc) using the "Bravais Lattices" drop down
box or<br>
the ionic structures using the "Other Compounds" drop down box.<br>
<br>
It's easiest to understand things if you click the "All atoms"
button. <br>
Ask for more than 1 unit cell when trying to see the nearest
neighbors <br>
(coord. #). Also, for the ionic compounds it's much easier to see
the <br>
nearest neighbors if you click on "Connect Atoms" toward the bottom
<br>
of the window (you sometimes have to click it twice). <br>
<br>
Also, look at the links I have for ch 11/12 ("Notes" link). I have
the three<br>
unit cell calculation examples done in lecture. The table given in
the notes<br>
with the info about the unit cells for identical particles
(including packing) and<br>
a table for the 4 ionic structures in the notes (with the info you
should know<br>
in <font color="#ff0000">red</font>). The links for these last two
things were given above.<br>
<br>
Also, look at the last page of the chapter 11 (12) notes. You will
find a table<br>
summarizing the 4 types of solids and their properties. This can be
found<br>
on my class web page ("Notes" link),<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/notes/Table_13-10_solids_no_lines.pdf"><b>Types
of Solids and Their Properties</b></a><br>
<br>
<br>
I hope this makes sense. <br>
<br>
Dr. Zellmer
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