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The Group 14 Elements

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Title: The Group 14 Elements


1
Chapter 14
  • The Group 14 Elements

2
Group 14 Elements
  • Carbon
  • nonmetal
  • Silicon and Germanium
  • semimetals
  • Tin and Lead
  • weakly, electropositive metals

3
Group 14 Properties
  • Ability to form network covalent bonding and to
    catenate

Carbon (graphite)
Dichlorodimethyltin(IV)
4
Group Trends
  • Melting and boiling points

5
Oxidation States
  • Multiple oxidation states are common
  • 4 for all the elements
  • covalent bonding
  • CO2
  • -4 for C, Si, and Ge
  • covalent bonding
  • CH4
  • 2 for Sn and Pb
  • ionic bonding
  • PbF2

6
Stability of Oxidation States
  • Frost diagram

Most stable? Most reducing? Most oxidizing?
7
Carbon
  • Three common allotropes
  • Diamond
  • Graphite
  • Fullerenes and carbon nanotubes

8
Diamond
  • Covalent network of tetrahedrally, arranged
    covalent bonds

9
Diamond History
  • Graphite and diamond were thought to be two,
    different substances
  • In 1814, Humphry Davy burned his wifes diamond
    to prove it was indeed carbon
  • C(s) O2(g) ? CO2(g)

10
Diamond

  • Electrical insulator
  • Very good thermal conductor
  • High melting point
  • 4000C


Regular diamond (cubic)
Lonsdaleite (hexagonal)
11
Diamonds in Nature
  • Found predominantly in Africa
  • Zaire is the largest producer
  • 29
  • Russia
  • 22
  • South Africa is the largest in terms of
    gem-quality
  • 17

12
Diamonds in Nature
  • Crater of Diamonds State Park
  • Murfreesboro, Arkansas
  • http//www.craterofdiamondsstatepark.com/

13
Synthetic Diamonds
  • Can make synthetic diamonds from graphite by
    adding heat (1600C) and pressure (5 GPa)

Tracy Hall GE
14
Synthetic Diamonds
  • Thin films of diamonds can be made at low
    temperatures

Diamond Jet Reactor
15
Synthetic Diamonds
  • New methods have become available to produce more
    gem-quality stones

16
Diamond Uses
  • Drill bits and saws
  • Surgical knife coatings
  • Computer chip coatings
  • Jewlery

17
Graphite
  • Hexagonal layers of covalently bound carbon
  • similar to benzene
  • delocalized pi system

18
Graphite Layers
  • Very weak interactions between the layers
  • 335 pm interlayer distance
  • van der Waals radius
    is 150 pm
  • abab arrangment

19
Graphite Properties
  • Excellent conductor in two dimensions
  • due to the electron delocalization
  • Excellent lubricant
  • sheets slide
  • Absorber of gas

20
Graphite Reactivity
  • More thermodynamically stable than diamond
  • More kinetically reactive than diamond
  • Forms intercalation compounds

21
Graphite Sources
  • Mining
  • China
  • Siberia
  • North and South Korea

22
Graphite Production
  • Acheson Process

2500C, 30 hours
23
Graphite Uses
  • Lubricants
  • Electrodes
  • Lead pencils
  • clay mixtures
  • hard mixtures 2H
  • soft mixtures HB

24
Fullerenes
  • Carbon atoms arranged in a spherical or
    ellipsoidal structure
  • five and six-membered rings

C70
C60, Buckminsterfullerene
25
Fullerenes
  • Named after R. Buckminster Fuller

R. Buckminster Fuller (1895-1983)
Buckminster Fullers Dome 1967 Montréal Expo
26
Discovery of Fullerenes
  • David Huffman and Wolfgang Krätschmer
  • 1982

27
Discovery of Fullerenes
  • Kroto, Curl, and Smalley

28
Discovery of Fullerenes
  • Kroto, Curl, and Smalley

29
Fullerene Production
  • Huffman and Krätschmer


30
Fullerene Properties
  • very weak intermolecular forces
  • sublime when heated
  • soluble in most nonpolar solvents
  • give bright colors in solution

31
Fullerene Properties
  • C60 crystal lattice (fcc)
  • low density, 1.5 g/cm3
  • non-conductors of electricity
  • strong absorber of light

32
Fullerene Chemistry
  • Interstitial
  • superconductors

Rb3C603- superconductor
33
Fullerene Chemistry
  • Metal encapsulation
  • Li_at_C82
  • He_at_C60

34
Fullerene Chemistry
  • Reaction with gases
  • C60(s) 30F2(g) ? C60F60(s)

35
Cluster Sizes
  • Many different sizes

36
Carbon Nanotubes
  • Sumio Iijima
  • 1991

37
Nanotube Types
  • Single-walled (SWNT)
  • Multi-walled (MWNT)

38
Nanotube Properties
  • excellent conductor
  • molecular storage

39
Impure Carbon
  • Amorphous carbon (coke)
  • made by heating coal in an inert atmosphere
  • mostly graphite with some hydrogen impurities
  • used in iron production
  • removes oxygen
  • 5 x 108 tons per year

40
Impure Carbon
  • Carbon black
  • fine, powdered carbon
  • 3.65 x 109 tons annually

41
Impure Carbon
  • Activated carbon
  • high surface area
  • 103 m2/g
  • removes impurities from organic reactions
  • decolorizes chemicals

42
Carbon Isotopes
  • Three isotopes
  • carbon-12 (98.89 )
  • carbon-13 (1.11 )
  • carbon-14 (0.0000001)
  • radioactive
  • t1/2 5.7 x 103 years

43
14C Radioactive Dating
44
Carbon Chemistry
  • Two important properties
  • catenation
  • a bonding capacity greater than or equal to 2
  • an ability of the element to bond to itself
  • a kinetic inertness of the catenated compound
    toward or molecules and ions
  • multiple bonding

45
Catenation
  • An ability of an element to bond with itself

46
Bond Energies
  • Important in determining the reactivity and/or
    relative stabilities of products
  • CH4(g) 4F2(g) ? CF4(g) 4HF(g)
  • not
  • CF4(g) 4HF(g) ? CH4(g) 4F2(g)

47
Carbides
  • Binary compounds of carbon with more
    electropositive elements
  • typically hard with high melting points
  • three types
  • ionic
  • covalent
  • metallic

48
Ionic Carbides
  • Formed by the most electropositive elements
  • alkali and alkaline earth metals
  • aluminum
  • Only reactive carbides
  • Na2C2(s) 2H2O(l) ? 2NaOH(aq) C2H2(g)
  • Al4C3(s) 12H2O(l) ? 4Al(OH)3(s) 3CH4(g)

49
Covalent Carbides
  • Few examples
  • silicon carbide and boron carbide
  • only important nonoxide ceramic
  • 7 x 105 tons produced annually

SiO2(s) 3C(s) ? SiC(s) 2CO(g)
50
Covalent Carbides
  • Silicon carbide uses
  • grinding and polishing agents
  • high-temperature materials applications
  • mirror backings
  • body armor

51
Moissanite
  • SiC
  • hexagonal
  • similar to lonsdaelite and ZrO2

SiC
C
ZrO2
52
Metallic Carbides
  • Formed with transition metals
  • carbon atoms fit in the octahedral interstices in
    the metal lattice (interstitial carbides)
  • close-packed structure
  • 130 pm metallic radius
  • shiny luster
  • conduct electricity
  • hard and high melting point
  • chemical resistance

53
Metallic Carbides
  • Tungsten carbide
  • 20,000 tons produced annually
  • used in cutting tools

54
Metallic Carbides
  • Fe3C
  • cementite

55
Carbon Monoxide
  • Colorless, odorless gas
  • Very poisonous
  • 300-fold greater affinity for hemeglobin than
    oxygen

56
Carbon Monoxide
  • Carboncarbon triple bond
  • 1070 kJ/mol
  • 1.11 Å bond length

57
Carbon Monoxide Production
  • Incomplete combustion
  • CH4(g) 2O2(g) ? CO2(g) 2H2O(l)
  • CH4(g) 3/2O2(g) ? CO(g) 2H2O(l)
  • Dehydration of formic acid
  • HCOOH(l) H2SO4(l) ? H2O(l) CO(g) H2SO4(aq)

58
Carbon Monoxide Reactivity
  • With oxygen
  • 2CO(g) O2(g) ? 2CO2(g)
  • With halogens
  • CO(g) Cl2(g) ? COCl2(g)

phosgene
59
Phosgene
  • blister agent

60
Carbon Monoxide Reactivity
  • With sulfur
  • CO(g) S(s) ? COS(g)
  • As a reducing agent
  • Fe2O3(s) 3CO(g) ? 2Fe(l) 3CO2(g)

61
Carbon Monoxide Reactivity
  • With hydrogen
  • CO(g) 2H2(g) ? CH3OH(g)
  • OXO process
  • CO(g) C2H4(g) H2(g) ? C2H5CHO(g)
  • 10 million tons of chemicals synthesized using a
    similar process

62
Carbon Monoxide Reactivity
  • With transition metals
  • highly toxic
  • used for preparation of other transition metal
    complexes
  • Mo(s) 6CO(g) ? Mo(CO)6(s)

63
Carbon Dioxide
  • Dense, colorless, odorless gas
  • low reactivity
  • will not combust
  • 2Ca(s) CO2(g) ? 2CaO(s) C(s)

64
Carbon Dioxide
  • No liquid phase at atmospheric pressure
  • sublimes

Water
Carbon Dioxide
65
Carbon Dioxide Use
  • 40 million tons in the U.S. annually
  • 50 in refrigerant applications
  • 25 in the soft drink industry
  • 25 in the aerosol, life raft, and
    fire-extinguishing industries

66
Carbon Dioxide Sources
  • Byproduct of manufacturing processes
  • ammonia, molten metals, cement, sugar
    fermentation
  • Reaction of an acid with a carbonate
  • 2HCl(aq) CaCO3(s) ? CaCl2(aq) H2O(l) CO2(g)

67
Carbon Dioxide Testing
  • Limewater test
  • CO2(g) Ca(OH)2(aq) ? CaCO3(s) H2O(l)
  • CO2(g) CaCO3(s) H2O(l) ? Ca2(aq) 2HCO3-(aq)

68
Carbonic Acid
  • Used to carbonate soft drinks
  • H2CO3(aq) H2O(l) ? H3O(aq) HCO3-(aq)
  • HCO3-(aq) H2O(l) ? H3O(aq) CO32-(aq)

69
Carbon Dioxide Reactivity
  • With bases
  • 2KOH(aq) CO2(g) ? K2CO3(aq) H2O(l)
  • K2CO3(aq) CO2(g) H2O(l) ? 2KHCO3(aq)

70
Introduction
  • A supercritical fluid (SCF) is any substance at a
    temperature and pressure above its critical
    values
  • Critical temperature of a compound is defined as
    the temperature above which a pure, gaseous
    component cannot be liquefied regardless of the
    pressure applied.
  • Critical pressure is defined as the vapor
    pressure of the gas at the critical temperature.

71
Introduction
  • The temperature and pressure at which the gas and
    liquid phases become identical is the critical
    point.
  • In the supercritical environment only one phase
    exists.
  • The fluid, as it is termed, is neither a gas nor
    a liquid and is best described as intermediate to
    the two extremes.
  • This phase retains the solvent power common to
    liquids as well as the transport properties
    common to gases.

72
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Table 1. Comparison of physical and transport
properties of gases, liquids and SCFs.  
78
What does scCO2 look like?
  • Here we can see the seperate phases of carbon
    dioxide. The meniscus is easily observed.

79
What does scCO2 look like?
  • With an increase in temperature the meniscus
    begins to diminish.

80
What does scCO2 look like?
  • Increasing the temperature further causes the gas
    and liquid densities to become more similar. The
    meniscus is less easily observed but still
    evident.

81
What does scCO2 look like?
  • Once the critical temperature and pressure have
    been reached the two distinct phases of liquid
    and gas are no longer visible. The meniscus can
    no longer be seen. One homogenous phase called
    the "supercritical fluid" phase occurs which
    shows properties of both liquids and gases.

82
Extraction and Chromatography
  • 1970s were first used commercially
  • to decaffeinate coffee
  • Media have been used successfully to extract
    analytes from a variety of complex compounds
    through manipulation of system pressure and
    temperature.
  • By comparison, conventional methods (e.g.,
    Soxhlet extraction and vacuum isolation) are more
    complicated and time and energy intensive.

83
Extraction and Chromatography
  • The limiting property of sc-CO2 is that it is
    only capable of dissolving nonpolar organic-based
    solutes.
  • The addition of small amounts of a cosolvent such
    as acetone has been shown to significantly
    improve the solubility of relatively polar
    solutes.

84
Micelle Formation
  • Solubility of ionic compounds such as aqueous
    metal salts has been enhanced through inverse
    micelle formation using fluorinated surfactants.

85
Extraction
  • SCF extraction has also been applied to
    environmental remediation such as removing
    organics from water and soil.
  • To extract metal contaminants, a chelating agent
    is commonly added to the fluid, with the soluble
    metal complex being removed from the SCF
    following system depressurization.

86
Other Uses for scCO2
  • Catalysis
  • Materials synthesis
  • Chemical vapor deposition (CVD)

87
The Greenhouse Effect
  • Radiation trapping

88
Molecular Vibrations
  • Only heteronuclear, polyatomic molecules absorb
    infrared energy
  • dinitrogen, dioxygen, and argon do not

89
Earths Infrared Spectrum
90
Sources of Carbon Dioxide
  • Volcanoes
  • Burning of vegetation
  • Burning of fossil fuels

91
Carbon Dioxide Levels
92
Kyoto Protocol
  • Results of a meeting of 161 countries in 1998 on
    greenhouse emissions
  • Aims
  • reduce the emmissions of carbon dioxide, methane,
    dinitrogen oxide, hydrofluorocarbons,
    perfluorocarbons, and sulfur hexafluoride
  • reduce emissions by 5 of those in 1990

93
Kyoto Protocol
  • Solutions to the problem
  • place a greater dependence upon the generation of
    power from non-carbon-based fuels
  • wind, water, and nuclear power
  • use carbon resources in a more efficient manner
  • hybrid-fuel passenger vehicles
  • biodiesel fuels

94
Kyoto Protocol
  • Other solutions
  • if an industrialized nation helps a devloping
    country reduce its emissions, then that
    industrialized country can count part of the
    benefits towards its own reduction goal
  • emission-reduction credits are tradable like
    stocks
  • removing greenhouse gases by increasing forestry
    can also be credited

95
Kyoto Protocol
  • Signed by all nations except the U.S.
  • U.S. produces 25 of the worlds emissions

96
Carbon Dioxide Sequestration
  • Storage of emitted carbon dioxide
  • increasing photosynthetic absorption
  • planting trees
  • iron enrichment in seawater
  • developing chemical technology to convert carbon
    dioxide into useful products
  • limited due to quantities produced and energy
    needed

97
Carbon Dioxide Sequestration
  • Storage of emitted carbon dioxide
  • storing the gas in underground geological
    formations
  • separating CO2 from methane in natural gas
  • pumping CO2 into oceans

98
Carbon Dioxide Sequestration
  • Pumping into oceans
  • will greatly decrease the pH of the oceans
  • CO2(aq) H2O(l) ? H3O(aq) HCO3-(aq)
  • CO2(aq) CO32-(aq) ? 2 HCO3-(aq)

99
Hydrogen Carbonates
  • Prepared by reaction of the carbonate with carbon
    dioxide and water
  • CaCO3(s) CO2(aq) H2O(l) ? Ca(HCO3)2(aq)
  • All hydrogen carbonates decompose to the
    carbonate upon heating
  • Ca(HCO3)2(aq) ? CaCO3(s) CO2(aq) H2O(l)

100
Hydrogen Carbonates
  • Amphoteric
  • HCO3-(aq) H(aq) ? CO2(g) H2O(l)
  • HCO3-(aq) OH-(aq) ? CO32-(aq) H2O(l)

101
Carbonates
  • Basic in solution due to hydrolysis
  • CO32-(aq) H2O(l) ? HCO3-(aq) OH-(aq)
  • washing soda

102
Carbonates
  • bonding

103
Carbonates
  • Molecular orbitals
  • 1 total pi bond
  • 1/3 per oxygen atom

104
Carbonates
  • Properties
  • most insoluble
  • except alkali metal and ammonium carbonates
  • most decompose upon heating to give the oxide
  • CaCO3(s) heat ? CaO(s) CO2(g)
  • for weakly electropositive metals,
  • Ag2CO3(s) heat ? Ag2O(s) CO2(g)
  • Ag2O(s) heat ? 2Ag(s) 1/2O2(g)

105
Carbon Disulfide
  • Sulfur analogue of carbon dioxide
  • colorless, highly flammable, low-boiling
  • sweet smell when pure, foul when not
  • highly toxic
  • CH4(g) 4S(l) heat ? CS2(g) 2H2S(g)
  • used in the production of cellophane, rayon
    polymers, and carbon tetrachloride
  • 1 million tons annually

106
Carbonyl Sulfide
  • SCO, or COS
  • most abundant sulfur-containing gas in the
    atmosphere
  • 5 x 106 tons
  • low reactivity
  • only sulfur-containing gas to penetrate the
    stratosphere

107
Carbon Tetrahalides
  • Carbon tetrahedrally bound to four halogen
    molecules
  • properties are dependent upon the dispersion
    forces present
  • CF4 is a colorless gas
  • CCl4 is a dense, oily liquid
  • CBr4 is a pale, yellow solid
  • CI4 is a bright, red solid

108
Carbon Tetrachloride
  • good, nonpolar solvent
  • very carcinogenic
  • was used in fire extinguishers
  • oxidized to form poisonous carbonyl chloride,
    COCl2
  • greenhouse gas and ozone depleter

109
Carbon Tetrachloride
  • Production
  • FeCl3 catalyzed reaction
  • CS2(g) 3Cl2(g) ? CCl4(g) S2Cl2(l)
  • CS2(g) 2S2Cl2(l) heat ? CCl4(g) 6S(s)
  • reaction of methane with chlorine
  • CH4(g) 4Cl2(g) ? CCl4(l) 4HCl(g)

110
Carbon Tetrachloride
  • Reactivity
  • very inert
  • CCl4(l) 3H2O(l) ? H2CO3(aq) 4HCl(g)
  • ?G -380 kJ/mol
  • SiCl4(l) 3H2O(l) ? H2SiO3(aq) 4HCl(g)
  • ?G -289 kJ/mol

111
Chlorofluorocarbons
  • First prepared in 1928 by GM chemist Thomas
    Midgley, Jr.
  • CCl2F2
  • very good refrigerant
  • completely unreactive
  • nontoxic

112
Chlorofluorocarbons
  • Nomenclature
  • The first digit represents the number of carbon
    atoms minus one
  • The second digit represents the number of
    hydrogen atoms plus one
  • The third digit represents the number of fluorine
    atoms
  • Structural isomers are distinguished by a,b,
    etc

113
Chlorofluorocarbons
  • Nomenclature

114
Chlorofluorocarbons
  • Ozone depleters
  • Cl O3 ? O2 ClO
  • ClO ? Cl O
  • Cl O3 ? O2 ClO
  • ClO O ? Cl O2

115
CFC Alternatives
  • HFC-134a
  • CF3CH2F
  • costly to produce
  • current equipment needs to be replaced
  • greenhouse gas

116
Methane
  • CH4
  • colorless, odorless gas
  • only detectable by addition of impurities
  • major source of thermal energy (natural gas)
  • CH4(g) 2O2(g) ? CO2(g) 2H2O(g)
  • fastest growing gas in the atmosphere
  • cattle and sheep by-products

117
Cyanides
  • HCN
  • toxic but useful
  • over 1 million tons annually
  • Almond-like odor
  • liquid at room temperature due to hydrogen bonding

118
HCN Production
  • Degussa Process
  • CH4(g) NH3(g) Pt ? HCN(g) 3H2(g)
  • Andrussow Process
  • 2CH4(g) 2NH3(g) 3O2(g) ? 2HCN(g) 6H2O(g)

119
Andrussow Process
120
Hydrogen Cyanide
  • Acidic in water
  • HCN(aq) H2O(l) ? H3O(aq) CN-(aq)
  • Neutralization produces sodium cyanide
  • HCN(aq) NaOH(aq) ? H2O (l) NaCN(aq)
  • used in the extraction of gold and silver from
    ores

121
Hydrogen Cyanide Uses
  • 70 in polymer production
  • Nylon
  • Melamine
  • Acrylic plastics
  • 15 in NaCN production

122
Hydrogen Cyanide History
  • The Peoples Temple

123
Hydrogen Cyanide Gas Chambers
  • 2NaCN(aq) H2SO4(aq) ? Na2SO4(aq) 2HCN(g)
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