1. Solid State Electrical Conductivity & Reactivity
Edward A. Mottel
Department of Chemistry
Rose-Hulman Institute of Technology

2. Solid State Electrical Conductivity
Solid ionic compounds are poor electrical conductors.
Mobile charges (ions or electrons) are needed for electrical conductivity.
The difference in energy of bonding and antibonding orbitals in a solid can explain many electrical properties.

3. Bonding Band Theory Si silicon (diamond structure) directional
localized bonds Si
4 Si atoms
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4. Bonding Band Theory directional localized bonds Si 4 Si atoms
conduction band
band gap
valence band
for silicon
the valence band is full
the conduction band is empty
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5. Smaller gap for heavier elements
Band Gap
carbon
(diamond)
silicon
germanium
tin
Smaller gap for heavier elements
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6. Band Gap C diamond - insulator Si semimetal, semiconductor Ge Sn
graphite has a different
structure than diamond
and is a conductor C Si Ge Sn
diamond - insulator
semimetal, semiconductor
grey tin - metallic, conductor
Smaller gap for heavier elements
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7. Bonding Covalent and Metallic Bonding
directional
localized bonds C
4 C atoms
conduction band
no band gap
valence band
Insulator
Metallic Conductor
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8. Density of States Insulator Semiconductor Metal overlapping mo’s in
extended structure
conduction band
valence band
levels are
not uniformly spaced
Insulator
Semiconductor
Metal
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9. Conductivity
e-
metal
semiconductor
insulator T  
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10. Band Gap average T2 > T1 Energy 
number of electrons
T2 > T1
free electrons or holes move charge
higher temperature puts more e- in conduction band

11. Conductivity
e-
metal
semiconductor
insulator T  
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12. Elements in SemiconductorsB C N O F Al Si P S Cl Cu Zn Ga Ge As Se Br Ag Cd In Sn Sb Te I
Intrinsic: Si, Ge, Fe3O4
Alloys: GaP, GaAs, ZnS, CdS, CdSe, SiC
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13. Doped Semiconductors n-type semiconductor 1% As in Ge p-type
excess mobile
electrons
p-type
semiconductor
1% Ga in Ge
excess mobile
holes
conduction band
valence band
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14. Diode n-type p-type a combination of an n-type semiconductor and a
p-type semiconductor
that allows current flow
in a preferred direction
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15. Diode - + n-type p-type e- flow can occur with e- moving to
more stable
energy levels
Both conduct
because there are
mobile electrons or holes
and locations to move to. e-
Battery provides e-
on one side and
drain on the other side. - e- +
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16. Diode - + n-type p-type Current flow in the
reverse direction requires e-
move to higher energy levels,
and occurs only with
large applied potentials
(breakdown voltage).
The semiconductors are
charge neutral,
and additional charge
will build up in the valence band
preventing significant
current flow. - + e- e-
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17. Diode
Current 
 Reverse Bias
Forward Bias 
Applied Voltage

18. Light Emitting Diodes band gap  = E h = c  wavelength (color)
h = 6.62 x J·s·molecule-1
c = 3.00 x 108 m·s-1

20. Solid State Photoreactions
Ag+
Br-
Ag+
Br-
Ag+
Br- h
Br-
Ag+
Br-
Ag+
Br-
Ag+
Ag+
Br-
Ag+
Br-
Ag+
Br-
Br-
Ag+
Br-
Ag+
Br-
Ag+
Ag+
Br-
Ag+
Br-
Ag+
Br-
Br-
Ag+
Br-
Ag+
Br-
Ag+

21. Solid State Photoreactions
Ag+
Br-
Ag+
Br-
Ag+
Br-
Br-
Ag+
Br-
Ag+
Br-
Ag+
Ag+
Br-
Ag+ Br Ag
Br-
Br-
Ag+
Br-
Ag+
Br-
Ag+
Ag+
Br-
Ag+
Br-
Ag+
Br-
Br-
Ag+
Br-
Ag+
Br-
Ag+

22. AgBr(s)  Ag(s) + ½ Br2(l)
½ Br2(g)
325 kJ·mol-1
Ag+(g)
Br-(g)
Ag(g)
Ag(l)
Ag(s) + Br2(l)
100 kJ·mol-1
AgBr(s)
major energy requirement is reverse of EA of Br-
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23. AgBr(s)  Ag(s) + ½ Br2(l)
E = 325,000 J·mol-1
 = E h = c 
h = 6.62 x J·s·molecule-1
c = 3.00 x 108 m·s-1
mol = 6.02 x 1023 molecules
causes sun darkening glasses to turn darker.
 = hc E
= 3.68 x 10-7 m = 3680 Å
(near uv)
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24. 1-2-3 Superconductor YBa2Cu3O7
barium
yttrium
copper
oxygen

25. Resistivity metal superconductor resistivity resistivity temperatureTc

26. Superconductivity

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28. Heavier Members of a Family tend to form single bonds
silicon dioxide
quartz, glass, sand C O
carbon dioxide
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29. Si
silicon
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