Exam 2 Workbook 1 due

1
Announcements General Info
Exam 2 Workbook 1 - due Will post on the dynamic
course website - download! Finish Solid State
Chemistry (12.6) Will have enough to complete
the lab Exam 2 Friday 02/22 Chapters 7, 8, 9,
12.6 (no conductivity) No class tomorrow!
2
Solid State
Amorphous Solids are structures with poorly
defined shapes due to the atoms/molecules lacking
order (non-crystalline). examples glass,
rubber, plastics, charcoal Crystalline Solids
are structures with well defined shapes due to
the highly ordered arrangement of the
atoms/molecules. We will learn about the
forces that comprise crystalline solids on
Tuesday. They include Van der Waals Hydrogen
Bonds Ionic Bonds Covalent Bonds Metallic Bonds
3
Summary of Cubic Unit Cells
FCC
BCC
SC
4
2
1
Net atoms
4r/(v3)
2r
Edge length
2(v2)r
68
52
74
Packing Efficiency
4
Packing Identical Spheres
Figure 12.28 (continued)
closest packing of first and second layers

• abab pattern
• 74 efficiency

• abcabc pattern
• 74 efficiency

5
Summary
6
Types of Crystalline solids - cover bonding on
Tuesday
Atomic Solids are structures with individual
atoms held together by dispersion forces. Nobel
gases only! Molecular Solids are structures
with collections of individual molecules
(dipole-dipole, dispersion, and hydrogen
bonding). Ionic Solids are structures with
cations and anions held together by electrostatic
attractions (ionic bonds). The metal transfers
electrons to the nonmetal. Cations tend to be
smaller anions tend to be larger. Metallic
Solids are structures with metal cations held
together by a sea of valence electrons (metallic
bonds). The bonding electrons are highly
mobile. Alloys are homogeneous mixtures of two
or more metals/semi-metals (more an extension of
metallic solids). Network (Covalent) Solids are
structures with atoms held together covalently
throughout the solid (covalent bonds).
7
Metallic Radii Problem
Iridium has an FCC unit cell, with a density of
22.56 g/cm3. What is the atomic radius of Ir?

• Step 1 Density (d) of the unit cell 22.56
  g/cm3 massunit cell / volumeunit cell
• Step 2 Mass of 1 mol Ir 192.2 g, so mass of 1
  atom
• 192.2 g/mol / 6.022 x 1023 atoms/mol 3.19 x
  1022 g/atom
• Step 3 FCC has 4 atoms/unit cell, so massunit
  cell 3.19 x 1022 x 4 1.28 x 1021 g
• Step 4 Volumeunit cell mass/d 1.28 x 1021 g
  / 22.56 g/cm3 5.66 x 1023 cm3
• Step 5 V (edge length)3, so edge length V1/3
  3.84 x 108 cm 2v(2)r
• Step 6 Solve for r!
• r 3.84 x 108 cm / (2v2) 1.36 x 108 cm
  1.36 x 1010 m
• (See also Sample Problem 12.4)