资源简介

(共93张PPT)
Group IV A or 14
Carbon, Silicon, Germanium, Tin, Lead
Carbon
Graphite
Diamond
Fullerene
Bucky Tube
Graphite --------------------------------> diamond
100 kbar, 1200~2800 K
Cr, Fe or Ni
Graphite
Soft and black and the stable,common,form of carbon.
Very light and resistant
More 2D like; sp2 Orbitals. Atom is at the corners of fused hexagon in parallel layers
Strong bonds within layers and weak bond between layers
Good conductor of electricity
Diamond
Abrasive
Gem
Diamond
Hard and transparent and the unusual form of carbon.
Strong thermal conductivity
More 3D like behavior; sp3 orbital. Atom is bound to four other carbon atoms in a regular repetitive pattern.
Strong covalent bonding in 3 dimensions
Bad electrical conductor
(Diamonds are not forever!!) It will turn into graphite (given time). (Faster if you heat it up or bombard it with high energy ions.)
Fullerenes C60
Discovered in 1985 by Harry Kroto
University of Sussex, England
Richard Smalley and Robert Curl Jr
Rice University, Texas
1996 Nobel Prize in Chemistry
H.Kroto R. Smalley R. Curl
Smalley's apparatus for generating and detecting buckyball.
Schematic of a mass spectrometer
“..in the field of Observation, chance only
favors the prepared mind”
Louis Pasteur
C60
Bucky Ball; fullerene
J.R. Heath, S.C. O'Brien, H.W. Kroto,
R.F. Curl, R.E. Smalley,
Nature 318 , 162, (1985)
Fullerene
C60
- A third allotropic form of very stable spheres(1985)
- Formed when graphite is evaporated in an inert atmosphere.
- Assumed C60 consists of 12 pentagons and 20 hexagons with carbon atoms at each corner, as a soccer ball.
- Names
New carbon ball
C60
Buckminsterfullerene
( R.Buckminster Fuller : The geodesic dome 1967 )
Buckyball
All have 12 pentagonal faces, 145.5 pm on a side.
C60 has 20 hexagonal faces, 139 pmT= 5K on a side.
The C=C between two pentagons is electron rich,
The pentagons themselves are electron poor.
The LUMO of C60 is triply degenerate.
Fullerides C60-1 to –6, C603- are superconducting below T = 28K.
Fullerenes may encapsulate metal atoms or small clusters. Clusters lose 3 electrons to the fullerene.
La @ C60 is La3+ @ C603-.
The Fullerenes – Molecular forms of Carbon
What is happening in current research with Buckyball
Model of C60 docked in the binding site of HIV-1 protease
Fullerene Pyrrolidine and Osmium Tetroxide derivatives of C60.
C50-containing soot ( 90 g) was synthesized in a modified graphite arc-discharge process in which 0.013 atm of CCl4 was added to 0.395 atm of helium. The products in the toluene extract from the soot were isolated with multistage high-performance liquid chromatography . and 2 mg of C50Cl10 with 99.5% purity was obtained.
The C50Cl10 thus obtained is moderately soluble in some organic solvents, e.g., carbon disulfide, toluene, and benzene, as a lemon yellow–colored solution.
Science, Vol 304, Issue 5671, 699 , 30 April 2004
Rational Side of Materials Chemistry:
Rational Doping:
C60 insulator Semiconductor Superconductor
La2CuO4
Magnetic insulator Bad Metal Superconductor
K
K3C60
Nanotubes C1,000,000 and beyond
Discoverer: Sumio Iijima
Carbon Nanotubes (CNT)
1991 multiwalled CNT
coaxial cylinders with a hollow core
1993 single-walled CNT
Roll up sheets of hexagons
Nanotubes C1,000,000 and beyond
Diameter ~ 1-30 nm
Length ~ microns
Interlayer Spacing
0.347 nm
Graphite interlayer
spacing 0.337 nm
IBM
Do C60 and CNT really exist
NUS Surface Science Laboratory
Seeing is believing
Yacobson and Smalley
Richard Smalley Image Gallery
Arc Discharge
Catalytic Decomposition
H, CH4 or CO
Temperature Programmable Furnace
Quartz Tube
Catalyst
CO/ CH4
CNT
Co/La2O3
600-750 oC
2CO
C + CO2
CH4
C + 2H2
2-dimensional hexagonal lattice of carbon
sp2 hybridized carbon atoms
Basis for C-60 (bucky balls), nanotubes, and graphite
Among strongest bonds in nature
What is graphene
A. K. Geim & K. S. Novoselov. The rise of graphene. Nature Materials Vol 6 183-191 (March 2007)
A Two dimensional crystal
In the 1930s, Landau and Peierls (and Mermin, later)showed thermodynamics prevented 2-d crystals in free state.
Melting temperature of thin films decreases rapidly with temperature -> monolayers generally unstable.
In 2004, experimental discovery of graphene- high quality 2-d crystals
Possibly, 3-d rippling stabilizes crystal
Representation of rippling in graphene. Red arrows are ~800nm long.
How to make graphene
Strangely cheap and easy.
Either draw with a piece of graphite, or repeatedly peel with Scotch tape
Place samples on specific thickness of Silicon wafer. The wrong thickness of silicon leaves graphene invisible.
Graphene visible through feeble interference effect. Different thicknesses are different colors.
Samples of graphene
Graphite films visualized through atomic force microscopy.
Transmission electron microscopy image
c) Scanning electron microscope image of graphene.
Electrons in graphene
Electrons in p-orbitals above and below plane
p-orbitals become conjugated(共轭的） across the plane
Electrons free to move across plane in delocalized（不受限制的） orbitals
Extremely high tensile strength（抗张强度）
http://en.wikipedia.org/wiki/Aromaticity
-Graphene and graphite are great conductors along the planes.
Synthesis of Graphene
Chemical Vapor Deposition (CVD)
thermal decomposition of hexagonal α-SiC
Combustion of Mg in CO2!
Electrolysis in Ionic Liquid
carbon fibers
Carbides
Preparation of Metal Carbides:
Direct combination of the elements or the metal oxide with carbon at high temperature.
Reaction of the heated metal with gaseous hydrocarbon.
Reaction of acetylene with electropositive metals in liquid ammonia.
Structure of Carbides
C4- methanide: produces predominantly CH4 on hydrolysis. eg:Be2C and Al4C3
C22-, acetylide (ethynide): alkali metals, M2IC2, alkaline earth metals,MIIC2, and the lanthanoids LnC2 and Ln2C3.
CaC2 + N2 CaCN2 + C @ 1000+ oC
石灰氮；碳氮化钙;碳酰亚氨钙；氰氨基钙
cyanamide - can be trimerized to melamine
Interstitial Carbide
Where the carbon-metal electronegativity difference is smaller, as in transition metal carbides, MxCy compounds are called interstitial carbides. eg., WC. Bonding is more covalent, properties are metallic.
Compounds of Carbon
Structure：
CO(6+8=14e-) and N2（2×7=14e-）
Isoelectronic, similar structure。
One bond
Two bond
:C O:
Oxides
Monooxide (CO)
:C O:
Properties of CO：
① as ligand，forming carbonyl complexes
Fe(CO)5, Ni(CO)4, Co2(CO)8
C as coordinating atom。
② Reductant：
③Highly toxic
Dioxide (CO2)
：O C O ：
structure：O=C=O
O
C=O bond length 124pm as in CH3--C--CH3
C O bond length 113pm
C-O bond length in CO2: 116pm
C：sp
Solid state:
Dry ice
Carbides
Direct Combination of the elements above
2000 C.
Reaction of the metal oxide with carbon at high temperatures.
Reaction of heated metal with gaseous hydrocarbon.
Reaction of acetylene with electropositive metals in liquid ammonia.
Carbonates
CO2 soluble in H2O，mostly as CO2 H2O，
A few as H2CO3
Structure of CO32-：
CO32-(6+3×8+2=32e-) and BF3(5+3×9=32e-)
are isoelectronic。
C：sp2
2-
-7
1
-
3
3
2
10
4.4
HCO
H
CO
H
×
=
+
+
K
11
-
2
-
2
3
-
3
10
4.7
CO
H
HCO
×
=
+
+
K
Thermal stability of carbonate：
H2CO3Thermal stability increases down a group
BeCO3 MgCO3 CaCO3 SrCO3 BaCO3
Dec T/℃ 100 540 900 1290 1360
Low thermal stability for transition metal carbonate
CaCO3 PbCO3 ZnCO3 FeCO3
Dec T /℃ 900 315 350 282
VE config. 8e_ (18+2)e_ 18e_ (9-17)e_
Why
[
]
2-
M
2+
MCO3 MO + CO2
r(M2+) more polarizing ，MCO3 less stable； M2+ with 18e_，(18+2)e_ ，(9-17)e_ electronic config. Higher polarzing power comparing with 8e_， reducing MCO3 stability.
Easily Polarizable
Solubility of carbonate：
soluble：Na2CO3 NaHCO3 K2CO3 KHCO3
100℃solubility 45 16 156 60
(g/100g H2O)　　　
2-
-
-
-
other carbonates (including Li) insoluble in H2O，bicarbonates more soluble than carbonates。
H-bond,dimer or polymer form
Hydrolysis of carbonates in H2O：
OH
HCO
O
H
CO
-
-
3
2
-
2
3
+
+
OH
CO
H
O
H
HCO
-
3
2
2
-
3
+
+
)
CO
(H
)
CO
(
3
2
2
W
2
3
1
K
K
K
=
-
)
CO
(H
)
CO
(
3
2
1
W
2
3
2
K
K
K
=
-
① metal ions with hydroxides as strong base form carbonates。
eg：Ba2+、Sr2+、Ca2+ and Ag+ etc。
Type of carbonate precipitates:
② metal ions with hydroxides as medium base form basic carbonates。
eg：Pb2+、Bi3+、Cu2+、Cd2+、Zn2+、Hg2+、Co2+、Ni2+ and Mg2+ etc。
③ metal ions that are easily hydrolysable or amphoteric form hydroxide precipitates.
eg：Al3+、Fe3+、Cr3+、Sn2+、Sn4+ and Sb3+etc。
(g)
3CO
(s)
Al(OH)
2
O
3H
3CO
Al
2
2
3
2
-
2
3
3
+
+
+
+
(g)
CO
(s)
CO
(OH)
Mg
O
H
2CO
2Mg
2
3
2
2
2
-
2
3
2
+
+
+
+
(g)
CO
(s)
CO
(OH)
Cu
O
H
2CO
2Cu
2
3
2
2
2
-
2
3
2
+
+
+
+
Intercalation compounds of graphite
Silicon
IBM Copper interconnects
Semiconductors
Germanium and Silicon form a diamond lattice.
Bonding electrons in Si and Ge are held less tightly than in C.
Compounds in which the electrical conductivity increases with increased temperature, light, or addition of impurities are semiconductors.
VB
CB
eg
eg
e- e- e- e- e-
h+ h+ h+ h+ h+
Low T
High T
-
+
n-type (Si + P)
p-type (Si + B)
diodes pn junction
transistor pnp or npn
CONVENTIONAL LIGHT-EMITTING DIODES
Atomic Semiconductor Devices (The Zerner Diode)
Limitations
Typical LED Materials
640-670nm Red GaAlAsP $0.40
525nm Green GaN $2.95
Blue SiC $1.29 and 430nm GaN $1.00
400-418nm Violet GaN $0.80
Tunability
Patterning
Quantum Confinement
High Cost of Fabrication
Cadillac DeVille LED taillights can illuminate up to
0.2 s faster than cold incandescent taillamps.
Tin
Known since 3000B.C.
Tin is one of the elements which has an alchemical symbol.
Tin is commonly available as the mineral cassiterite, SnO2.
Reduction with burning coal results in tin metal.
This was probably how tin was made by the ancients.
SnO2 + 2C Sn + 2CO
Isotopes of Tin
-Sn -Sn
13.2oC
“white” tin
Metallic in appearance.
Tetragonal structure.
Highly crystalline.
“grey” tin
Crumbly (brittle)
Cubic structure
Prolonged cooling causes conversion to alpha form.
Lead
Pb organ
Oxford, England.
PbS + 3/2O2 PbO + SO2
PbO + C Pb + CO
PbO + CO Pb + CO2
Isolation
Uses
Yellow and Red Pigments
Trends in Group 14 Bond Energies
The decrease in bond strength as one goes down the group is marked and modified only by p -d bonding.
d bonding diminishes: Si > Ge > Sn > Pb >> C. There are no germanium analogues to the silicones. The exceptional stability of the Si-O bond is not duplicated in the Ge-O bond.
Stability of the M(II) state: Pb >> Sn > Ge > Si > C.
Ability to catenate: C >> Si > Ge > Sn > Pb. For the alkane analogues: SinH2n+2 n = 8; GenH2n+2 n = 5.
Hydrides of germanium are not pyrophoric and are unaffected by acid/base, unlike the silanes. Hydrides of tin and lead are of marginal stability
Properties：
① Reaction with Base
② Reaction with HF
2.Silicic acid and silicates
H4SiO4 silicic
H2SiO3 metasilicic
xSiO2 yH2O polysilicic
Properties：
12
2
10
1
3
2
10
6
.
1
10
7
.
1
SiO
H
-
-
×
=
×
=
，
，
low solubility，biacid
K
K
Preparation：
Silica gel containing small amount of CoCl2will change color at different H2O contents。
Silicic acid as gel
Silica gel
-H2O
2NaCl
SiO
H
2HCl
SiO
Na
3
2
3
2
+
+
(g)
2NH
2NaCl
SiO
H
Cl
2NH
SiO
Na
3
3
2
4
3
2
+
+
+
soluble：Na2SiO3 、K2SiO3
insoluble: with characteristic color。
silicates
Si sp3
Tetrahedral arrangement of Si-O
silica
Structure of silica：
halides SiX4
SiF4 SiCl4 SiBr4 SiI4
State g l l s
hydrolysis：
Mp low high
Hydride (silane SinH2n+2)
property：
simplest：SiH4
pyrophoricity：
hydrolysis：
strong reductant：
low thermal stability：
Silicon Carbide（SiC）：
Hydroxides of Tin and Lead
HNO3or HAc
H+
standing
H+
-
2
6
]
[Sn(OH)
3
2
)
(s,
SnO
H
-
w
α
4
Sn
+
ex. OH-
ex. OH-
-
3
]
[Pb(OH)
2
)
(s,
Pb(OH)
w
2
Pb
+
ex. OH-
ex. OH-
-
2
4
]
[Sn(OH)
2
)
(s,
Sn(OH)
w
2
Sn
+
ex. OH-
ex. OH-
c-HNO3
)
(s,
SnO
H
-
Sn
3
2
Not sol in A or B
w
β
O
H
4NO
SnO
H
)
(
4HNO
Sn
2
2
3
2
3
+
+
+
c
β
-
Sn(II) as reductant
Identification of Sn2+,Hg2+
Identification Reaction of Bi3+
Sn
0.136
Sn
0.154
Sn
/V
2
4
A
-
+
+
E
-
Sn
0.91
]
[Sn(OH)
0.93
-
]
[Sn(OH)
/V
2
4
-
2
6
B
-
E
Pb(IV) as oxidant
Pb
0.58
PbO
0.25
PbO
/V
Pb
0.126
Pb
1.45
PbO
/V
2
B
2
2
A
-
-
+
E
E
O
H
NaCl
PbO
NaClO
Pb(OH)
2
2
2
+
+
+
2
2
-
4
2
2
O
2H
5Pb
2MnO
4H
2Mn
5PbO
+
+
+
+
+
+
+
2
2
2
2
O
2H
Cl
PbCl
)
4HCl(
PbO
+
+
+
c
2
2
2
4
4
2
2
O
2H
O
)
2Pb(HSO
SO
4H
2PbO
+
+
+
+
+
+
2
2
4
4
2
2
O
2H
O
2PbSO
SO
2H
2PbO
(Pb3O4)----red
can be seen as：
4HNO
PbO
Pb
3
4
2
+
O
2H
)
(
PbO
)
2Pb(NO
2
2
2
3
+
+
brown
(Pb2O3)：orange
seen as：PbO·PbO2
(PbO)：orange yellow
Other oxides of Pb
thermal decomp of .PbO2 ：
summary
oxidizing power，acidity
reducing power, basicity
basicity
acidity
Sn(OH)4
Pb(OH)4 PbO2
Sn(OH)2
Pb(OH)2
2.Salts of tin & lead
Hydrolysis：
(g)
CO
2
+
铅白
3.9
2
2
10
H
Sn(OH)
O
H
Sn
-
+
+
+
=
+
+
K
7.1
2
2
10
H
Pb(OH)
O
H
Pb
-
+
+
+
=
+
+
K
HCl
)
,
Sn(OH)Cl(s
O
H
SnCl
2
2
+
+
white
4HCl
]
[Sn(OH)
H
-
O
6H
SnCl
6
2
2
4
+
+
α
)
(s
CO
[Pb(OH)]
O
H
2CO
2Pb
3
2
2
-
2
3
2
+
+
+
soluble：Pb(NO3)2, Pb(Ac)2 --- toxic!
solubility：
insoluble：
PbCrO4 soluble in ex. amount of NaOH，different from BaCrO4。
Identification of Pb2+：
yellow
4
2
4
2
)
s,
(
PbCrO
CrO
Pb
+
-
+
Pb2+ Pb(OH) 3-
PbCl2(w) PbSO4(w) PbI2(y) PbCrO4 (y)
PbCl42- Pb(HSO4)2 PbI42- Pb2++Cr2O72-
c-HCl
c-H2SO4
I-
HNO3
OH-
Summary：
3.Sulfide of tin & lead
SnS(brown) SnS2(y) PbS(black)
SnS + 4HCl → H2SnCl4 + H2S
PbS + 4HCl → H2PbCl4 + H2S
SnS2 + 6HCl → H2SnCl6 +2H2S
PbS2
Insoluble in dilute HCl
Dissolution by coordination(in c-HCl)
SnS32- unstable decompose in acid。
Disolve in base (SnS, PbS insoluble)
Oxidation (SnS2,PbS insoluble)
PbS react with HNO3
（thiostannate）
O
4H
3S
2NO
)
3Pb(NO
8HNO
3PbS
2
2
3
3
+
+
+
+

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