Chapter 3 Molecular Shape and Structure
2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
CHAPTER 14 THE ELEMENTS: THE FIRST FOUR MAIN GROUPS
Beginning of the descriptive chemistry !
▶ Nanotechnology Æ 1 ~ 100 nm particles Æ Biosensor, Microscopic computers, Artificial bones, Light weight, strong materials
Fig. 14.1 The relative abundances of the principal elements. PREODIC TRENDS Congener (동족원소) ex. Li, Na, K, Rb, Cs, Fr 14.1 Atomic Properties
Fig. 14.2 Atomic radius Fig. 14.3 Ionization energy Fig. 14.4 Electronegativity Fig. 14.5 Polarizability
14.2 Bonding Trends ▶ Multiple bond formation Æ Depends on the size of atomic radii Ex. Period 2 elements form π -bond (effective overlap of p-orbitals) contrary to Period 3 and heavier elements Fig. 14.6 Overlapping of p-orbitals: (a) Period 3 and heavier elements. (b) Period 2 elements (π -bond) ▶ Periodic trend in bonding of main-group elements Æ Binary hydrides: Formulas directly related to the group number showing typical valences of the elements
CH4 (Group 14/IV), NH3 (Group 15/V), H2O (Group 16/VI), HF (Group 17/VII)
Fig. 14.7 Chemical formulas of hydrides vs. valences
1 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 ▶ Binary hydrides Saline hydrides (이온성 수소화물): s-block elements, white, high m.p., crystals, portable fuel, H– ∆ 2 K(sg) +⎯H2 ( ) ⎯→2 KH(s) Metallic hydrides: d-block elements, black, conducting powder, portable fuel ∆ 2 Cu(sg) +⎯H2 ( ) ⎯→2 CuH(s) Molecular hydrides: non-metal elements, low melting volatile Brønsted acid
NH3, HX, hydrocarbons
Fig. 14.8 The difference classes of the binary hydrogen compounds. Fig. 14.9 Hydrogen atoms of a metallic hydride in the interstices of the metallic lattice. ▶ Nonmetal oxides Acid anhydrides: non-metallic oxides
HO2 HO2 N25O ⎯⎯⎯→ HNO3, SO32⎯⎯⎯→ H SO4
HO Formal anhydrides of acids: CO ⎯⎯2 ⎯→ HCOOH
HYDROGEN 14.3 The Element
89% of all atoms in the universe (Fig.14.1) Present in water and hydrocarbons ▶ Preparation: (1) Electrolysis of water
hν (2) Water-splitting reaction: 2 H22O(lg) ⎯⎯→+2 H ( ) O2(g)
Ni (3) Reforming reaction: CH42()gg+⎯HO() ⎯→+CO()g3 H2(g)
Fe/Cu (4) Shift reaction: CO()gg+⎯H22O() ⎯⎯→CO()g+H2(g) Fig. 14.10 Mass of 10mL water (5) Reducing H+ ions from a strong acid: ≈ Mass of 100mL liquid H2. ++2 Zn(sa) +⎯2 H ( q) ⎯→+Zn (aq) H2 (g) ▶ Properties: Light, colorless, no smell, no flavor, liquefy at 20K ▶ Usage: Rocket fuel, Haber process
2 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
14.4 Compounds of Hydrogen
▶ Ionic hydrides: MH (M+H–) o − o+ E (H2 / H ) =−2.25 V cf. E (Na / Na) =−2.71 V Æ Strong reducing power
NaH(sl)H+⎯22O() ⎯→NaOH(aq)H+(g)Å portable H2 supply ▶ Hydrogen bonding O–H : Bond enthalpy = 463 kJ·mol–1 Oδδ−+⋅⋅⋅ H−O : Bond enthalpy = 20 kJ·mol–1
GROUP 1: THE ALKALIMETALS Na+/K+ couple Æ Concerted action and migration across the membrane Æ Consciousness Valence configuration: ns1
3 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 14.5 The Group 1 Elements ▶ Preparations: Electrolysis of molten rock salt (Downs process): Cathode: 2 Na+(melt) + 2 e– Æ 2 Na(l) Exposing molten KCL to sodium vapor:
750oC KCl(lg) +⎯Na( ) ⎯⎯→NaCl(s) +K(g)
▶ Properties: soft, lustrous, low m.p. & b.p.
Fig. 14.11 (a) Li (b) Na (c) K (d) Rb & Cs
Fig. 14.12 Melting points(oC) of alkali metals. ▶ Usage: Li-6 as a source of tritium (T) in thermonuclear weapons 64Li +⎯n ⎯→+T He Lithium-ion batteries 14.6 Chemical Properties of the Alkali Metals ▶ Strong reducing agent Å small E o values
2 Na(sl) +⎯2 H22O( ) ⎯→+2 NaOH(aq) H (g)
Fig. 14.13 Reactions with water: (a) Li (b) Na (c) K
4 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 ▶ Reaction with ammonia : ▶ Reaction with oxygen Electrons released from the metal fill the cavities formed by ammonia molecules. Æ ink-blue metal-ammonia solution
Fig. 14.15 Lithium oxide(LiO),,Sodium peroxide(Na2O2), Potassium superoxide(KO2)
Fig. 14.14 Sodium-ammonia solution
14.7 Compounds of Lithium, Sodium, and Potassium ◆ Lithium, Li Properties: Small size of Li+ ion Æ high polarizing power Æ forms bonds with high covalent character Æ strong ion-dipole interaction forming hydrates Usage
Ceramics, lubricants, medicine Li CO : bipolar disorder (조울증,躁鬱症) Fig. 14.16 An evaporation pond for brine from salt 2 3 lakes. (Blue dye for increasing heat absorption.) Lithium soap: high m.p., used in high-temp lubricant H-bomb, Li-Batteries ◆ Sodium, Na Sodium compounds: Low cost, high solubility in water
► NaCl: Used in producing Cl2 and NaOH ► NaOH: Soft, waxy, white, corrosive solid Produced by electrolysis of brine
− 2 Cl (aq) + 2 H2O(l)
electrolysis − ⎯⎯⎯⎯⎯→+Cl22(g) 2 OH (aq) +H (g)
► NaHCO3: baking soda
sodium hydrogen carbonate (sodium bicarbonate) Fig. 14.17 A diaphragm cell for the electrolytic − production of NaOH from brine. HCO3 (aq) +→HA(s aq) ⎯⎯→
− A (aq) ++H2O()l CO2 (g) ↑
Swelling of batter
5 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
◈ Kitchen Chemistry ▶ Baking powder = baking soda + acid salts (both high and low T) + corn starch
High T (slow-acting) acid salts:
sodium aluminum sulphate, AlNa(SO4)2·12H2O
sodium aluminum phosphate, NaAl3H14(PO4)8·4H2O or Na3Al2H15(PO4)8
sodium acid pyrophosphate, Na2H2P2O7
Low T (fast-acting) acid salts:
cream of tartar (or potassium hydrogen tartrate), KC4H5O6
monocalcium phosphate (or calcium acid phosphate), Ca(H2PO4)2
Corn starch: absorbs moisture
► Na2CO3·10H2O: washing soda Å alkaline
2+ 2− 2+ Ca (aq) +⎯CO33(aq) ⎯→CaCO (s) Å removing Ca ions from water
► Na2CO3, Soda ash Æ source of Na2O in glass industry
◆ Potassium, K
Minerals: Carnallite, KCl·MgCl2·6H2O; Sylvite, KCl Usage: Fertilizers
∆ 2 KNO3(s) ⎯⎯→2 KNO2(s) +O2(g) Å less hygroscopic (흡습성,吸濕性)
☺ Safety matches (1855) – Johan Lundstrom (서전,瑞典, 1815-1888)
match head: KNO3 + Sb2S3 + Pb3O4 + K2Cr2O7
rubbing surface: sand paper + red phosphorus + Sb2S3
GROUP 2: THE ALKALINE EARTH METALS
6 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 14.8 The Group 2 Elements
Fig. 14.18 1st- and 2nd-ionization energies (kJ·mol–1) of alkaline metal elements.
Fig. 14.19 Alkaline earth metals: (a) Be, (b) Mg, (c) Ca, (d) Sr, (e) Ba. ◆ Berylium, Be
Mineral: beryl, 3BeO·Al2O3·6SiO2 Æ emerald (beryl + impurity, Cr3+)
Preparation: Electrolytic reduction of molten BeCl2 Usage: Construction of missiles and satellites Window for X-ray tube Rigid Be-Cu alloy (Be added in interstitial sites of Cu metal)
Æ nonsparking tools (preventing explosion) Fig. 14.20 Emerald (녹주석,綠柱石) 5월 탄생석, ‘청순,淸純’ for oil refineries and grain elevators ◆ Magnesium, Mg
Seawater, Minerals (dolomite, CaCO3·MgCO3)
o Chemical reduction: dolomite Æ MgO ⎯ferro⎯⎯⎯⎯⎯silicon, 1200 C→ Mg
Ca(OH)2 HCl Electrolysis Electrolytic reduction: seawater ⎯⎯⎯⎯→ Mg(OH)2 ⎯⎯⎯→ MgCl2 ⎯⎯⎯⎯→ Mg
Burns vigorously in air, Reacts with water, CO2, N2 Usage: Airplane, automobiles Å light and tough Mg metal ◆ Calcium (Ca), Strontium (Sr), Barium (Ba) Preparation: Electrolysis
∆ Thermite process with Al: 3 BaO(ss) +⎯2 Al( ) ⎯→+Al23O (s) 3 Ba(s)
7 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 Reaction with water: Be does not react with water. Mg reacts with hot water. Ca reacts with cold water.
Ca(sl) +⎯2 H2O( ) ⎯→
2+− Ca (aq) ++2 OH (aq) H2 (g)
Colors of burning flames Ca (orange-red), Sr (crimson), Ba (yellow-green) Fig. 14.21 A gentle reaction of Ca with water.
14.9 Compounds of Beryllium and Magnesium
◆ Beryllium − 2− Reaction with a base: Be(sa) ++2 OH ( q) 2 H24O(l) ⎯⎯→+Be(OH) (aq) H2(g) beryllate ion Beryllium compound: Æ Very toxic 2+ Æ Be (strongly polarizing, small) Æ forming BeX4 unit Æ Chloride
600−800o C BeO(ss) + C( ) + Cl22(g) ⎯⎯⎯⎯→+BeCl (g) CO(g)
Be in BeCl2 : Lewis acid Æ accepts electron pairs from neighboring Cl atoms
Æ Forming a chain of tetrahedral BeCl4 units in solid
◆ Magnesium Forming ionic compounds Energy generation in living cells Æ Contraction of muscles ► MgO Æ obtained by heating hydroxide or carbonate Æ refractory (내화성,耐火性) m.p. 2800oC, cf. refractory index (굴절율) Æ good conductor for electricity Æ poor heat conductor Æ used for an insulator in electrical heaters
► Mg(OH)2 Æ basic Æ Forming a white colloidal suspension, “milk of magnesia” Å stomach antiacid
Reaction with acid Æ MgCl2 (purgative,설사제下劑) 8 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
► Antiacid, MgCO3 Æ causing ‘belch’ due to CO2
► ‘Epsom salt’, MgSO4·7H2O, Æ purgative Mg2+ prevents absorption of water by intestine ► Chlorophyll (엽록소,葉綠素) Capturing solar energy and channel it into photosynthesis Mg2+ keeps the plane of ring rigid Æ preventing the loss of energy into heat
14.10 Compounds of Calcium
► CaCO3 Colored marble due to impurity of iron cations Minerals: calcite (방해석,方解石), aragonite (산석,霰石) ► CaO (quicklime,생석회)
∆ CaCO32(ss) ⎯⎯→+CaO( ) CO (g)
2+ − CaO(s) +⎯H2O(l) ⎯→+Ca (aq) 2 OH (aq) Å highly exothermic reaction Å Fire !
∆ CaO(ss) +⎯SiO2( ) ⎯→CaSiO3(l) Å low m.p. slag in smelting of steel
► Ca(OH)2 : slaked lime (소석회,消石灰) Å commercial lime
Lime water, Ca(OH)2 (aq) Å used as a test for CO2
Ca(OH)22(aq) +⎯CO (g) ⎯→CaCO3(s) +H2O(l) Å suspension(현탁액,懸濁液) ☺suspense(迫眞感)
2+ Removing Ca ions in hard water containing Ca(HCO3)2. −−− 2 HCO33(aq) +⎯OH (aq) ⎯→+CO (aq) H2O(l) 2+ 2− Ca (aq) +⎯CO33(aq) ⎯→↓CaCO (s)
► Concrete Å Filler(충전재,充塡材) + Binder(접합재,接合材) Filler: gravels, polymer or vermiculite(질석,蛭石) pellets for lower density Binder: (Portland) cement Heating mixture of limestone, clay or shale(혈암,頁巖), sand, oxide (iron ore) Æ Hard pellets, ‘Clinkers(소괴,燒塊)’
~ mixture of CaO, Ca2SiO4, Ca3Al2(SiO4)3
Æ Ground with gypsum(석고,石膏), CaSO4·2H2O,
into powder Fig. 14.22 A surface of cement. Growth of inter- Mortar: cement : sand = 1 : 3 locking crystals as CO2 reacts with CaO and silica.
Reaction of CO2 in air with CaO and silica Æ Hard mass !
9 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 ► Rigid structure of living organisms:
Shells of shell fish: CaCO3 2+ Bones: Ca3(PO4)2 Æ Calcium (in bone) R Ca ions (in body fluids) Bone strength vs. Daily diet
Tooth enamel: hydroxyapatite(수산화인회석,水酸化燐灰石), Ca5(PO4)3OH Decay of tooth enamel by carboxylic acid:
+2+2− Ca54(PO )3OH(sa) +⎯4 H3O ( q) ⎯→+5 Ca (aq) 3 HPO4(aq) +5 H2O(l)
Coating against decay by fluoridation: more resistant fluorapatite(불화인회석)
−− Ca54(PO)3OH()sa+⎯F(q) ⎯→+Ca5(PO4)3F()sOH(aq)
Addition of fluoride (NaF) to tap water
Fluoridated toothpaste: SnF2 or sodium monofluorophospate (MFP, Na2FPO3)
GROUP 13/III: THE BORON FAMILY
First group of p-block: ns21np Oxidation states: B(III), Al(III), Tl(I), Tl(III)
14.11 The Group 13/III Elements ◆ Boron Hardness and low density High ionization energy Metalloid forming covalent bonds
Three valence electrons Æ incomplete octets Æ Forms electron-deficient compounds
Minerals : Na24B O7⋅ xH2O , borax(붕사,硼沙) ( x = 10 ) and kernite( x = 4 ) acid reduction by Mg Preparation: mineral ⎯⎯⎯→ oxide ⎯⎯⎯⎯⎯⎯⎯→ B
∆ B23O (ss) +⎯3 Mg( ) ⎯→ 2 B(s)+3 MgO(s)
Higher purity B : obtained by reduction of volatile compound on a heated Ta-filament
∆ 2 BBr32(gg) +⎯3 H ( ) ⎯→+2 B(s) 6 HBr(g)
10 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
▶ Allotropes (동소체,同素體) of boron: ► Gray-black, nonmetallic, high m.p. solid ► Dark brown powder with an icosahedral (정20면체) structure based on clusters of 12 atoms
◆ Aluminum Most abundant element in Earth’s crust
Minerals: bauxite ( Al23O ⋅=xxH2O, 1 ~ 3 ) ▶ Bayer process Å obtaining pure alumina
NaOH(aq) − bauxite ⎯⎯⎯⎯→ Al(OH)4 (aq)
CO2 (g) − ⎯⎯⎯→ Al(OH)33↓+ HCO
∆, 1200oC o ⎯⎯⎯⎯→ Al23O (s) Å m.p. 2050 C Fig. 14.23 Red tint of iron oxide in bauxite ore.
▶ Hall-Héroult Process (1886)
Electrolysis of melt of mixture of Al2O3 and o cryolite(빙정석,氷晶石), Na3AlF6 (m.p. 950 C)
Cathode reaction: Al3+−(melt) +⎯3 el⎯→ Al( ) (steel-lined vat) Anode reaction: 2 O2− (melt) + C(s,gr) − (graphite) ⎯⎯→+CO2 (ge) 4
Overall reaction: 4 Al32+−(melt) ++6 O (melt) 3 C(s,gr) ⎯⎯→+4 Al(lg) 3 CO ( ) 2
Fig. 14.24 Hall-Heroult process of producing Al 1 mol Al (2 cans) requires 80 hours of 1 A current ! by electrolysis. ▶ Amphoteric Al +3+ 2 Al(sa) +⎯6 H ( q) ⎯→+2 Al (aq) 3 H2 (g)
− − 2 Al(sa) ++2 OH ( q) 6 H24O(l) ⎯⎯→+2 Al(OH) (aq) 3 H2(g)
~ GaAs used in LED(light emitting diode): electricity Æ light ~ Thallium: rat poison
14.12 Group 13/III Oxides
▶ Boric acid (붕산,硼酸), B(OH)3 White solid, m.p. 171oC, antiseptic(소독약) and pesticide(살충제)
(OH)32B +⎯ : OH ⎯→(OH)3B −OH2 Å weak monoprotic acid
11 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
⎯⎯→ + − B(OH)32OH (aq) ++H2O(l)←⎯⎯ H3O (aq) B(OH)4(aq) , p9Ka = .14
▶ Boron oxide, B2O3 Anhydride of boric acid Used as a flux (융제,融劑), pyrex glass
▶ Alumina, Al2O3 ► α -alumina : very hard, stable, crystalline substance, corundum(강옥,鋼玉) Impure α -alumina : jewels or abrasive, emery(金剛砂)
Fig. 14.25 Gems of impureα -alumina: (a) Ruby (Cr3+), (b) Sapphire (Fe3+,Ti4+), (c) Topaz (Fe3+). ► γ -alumina : amphoteric
− − Al23O (sa) ++2 OH ( q) 3 H2O(l) ⎯⎯→ 2 Al(OH)4(aq)
+ 3+ Al23O (sa) ++6 H3O ( q) 3 H2O(l) ⎯⎯→2 Al(H2O)6(aq)
3+ ⎯⎯→ + 2+ Al(H26O) (aq) ++H2O(l)←⎯⎯ H3O (aq) Al(OH)(H2O)5(aq)
▶ Aluminum sulfate, Al2(SO4)3 Æ “papermaker’s alum”, 製紙工의 백반(白礬)
Al23O(sa)3+⎯ H2SO4(q) ⎯→+Al2(SO4)3(aq)3 H2O(l)
▶ Sodium Aluminate, NaAl(OH)4 Æ Used in water purification
3+ − Al (aq) +⎯3 Al(OH)43(aq) ⎯→ 4 Al(OH) (s)
Æ ppt with impurities ! Fig. 14.26 Formation a white fluffy ppt of Al(OH)3.
12 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 14.13 Nitrides and Halides ▶ Boron nitride, BN ~ fluffy, white slippery powder
∆ 2 B(sg) +⎯2 NH32( ) ⎯→+2 BN(s) 3 H (g)
Boron nitride ⎯⎯∆→ Borazon
Æ very hard, diamond-like crystalline form
▶ Boron trifluoride, BF3 Å catalyst
BO23(ss)++3 CaF2( ) 3 H2SO4(l)
∆ ⎯⎯→+2 BF34(gs) 3 CaSO ( ) +3 H 2O(l) Fig. 14.27 Structure of hexagonal boron nitride (BN). Stacked differently from graphite
▶ Boron trichloride, BCl3 Å catalyst
500o C B23O (ss) ++3 C( ) 3 Cl2(g) ⎯⎯⎯→+2 BCl3(g) 3 CO(g)
▶ Aluminum chloride, AlCl3 Å catalyst
2 Al(sg) +⎯3 Cl23( ) ⎯→ 2 AlCl (s)
Al23O (ss) ++3 C( ) 3 Cl2(g) ⎯⎯→+2 AlCl3(g) 3 CO(g)
sublimation, 192oC AlCl3 (ionic solid) ⎯⎯⎯⎯⎯⎯→ Al2Cl6 (g)
14.14 Boranes, Borohydrides, and Borides
▶ Boranes ~ binary compound with hydrogen
Diborane, B2H6, Decaborane, B10H14
◈ Borohydrides Æ anionic version of these compounds
► Sodium borohydride, NaBH4 Å Reducing agent
4 NaH +⎯BCl3⎯→NaBH4+3 NaCl in a nonaqueous solvent
−−−−o H23BO (aq) ++5 H2O(l) 8 e ⎯⎯→+BH4(aq) 8 OH (aq) , E =−1.24 V at pH = 13.
Reducing Ni2+ Æ Ni, ( E o =−0.23 V ) Å “Chemical plating” of nickel on nonconducting item
► Diborane, B2H6 Å colorless gas, bursts into flame in air
−− 4 BF34+⎯3 BH ⎯→+3 BF42 B2H6
13 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
B26H (gl) +⎯6 H2O( ) ⎯→+2B(OH)3(aq) 6 H2(g)
∆ BH26(gs)⎯⎯→+2 B() 3 H2(g)
★ Bonding in B2H6 # of valence electrons : 12 Æ Six bonds : Four B–H bonds + Two three-center bonds among B–H–B
GROUP 14/IV: THE CARBON FAMILY 14.15 The Group 14/IV Elements
Natural intelligence : C Artificial intelligence : Si, Ge Half-filled valence shells Æ nonmetal (C,Si), metalloid (Ge) metal (Sn,Pb) Electronic configuration: ns22np Sn : amphoteric
C: double bond, O=C=O Fig. 14.28 Group 14/IV elements: C, Si, Ge, Sn, Pb Si: network, –O–Si–O–
++2 Sn(sa) +⎯2 H32O ( q) ⎯→+Sn (aq) H (g) +2 H2O(l)
− 2− Sn(sa) ++2 OH ( q) 2 H24O(l) ⎯⎯→+Sn(OH) (aq) H2(g)
14 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
Silicon compounds : big Si atom, expansion of d-orbital Æ Lewis acids
Carbon compounds : small C atom, d-orbital unavailable Æ Lewis acid
Exception) C atom with multiple bonds
14.16 Different Forms of Carbon Soot, Carbon black, Activated carbon, Graphite, Diamond, Fullerene ◈ Allotropes of carbon ◆ Graphite sp2 hybrid orbitals Æ hexagonal network Delocalization of π − electrons Æ Electrical conductivity Used as electrodes in batteries Æ Slipperiness Used as the “lead (graphite+clay)” in pencil Obtained by passing a heavy electric current through rods of “coke” Fig. 14.29 Structure of hexagonal graphite. ABAB stacking. ◆ Diamond (1 carat = 200 mg = 0.2 g) sp3 hybrid orbitals Æ tetrahedral
Fig. 14.30 Tetrahedral structure of The largest diamond (7500 carat) Fig. 14.31 Phase diagram of carbon. diamond.
Natural diamond : embedded in a soft rock, ‘kimberlite’ Å Australia, Botswana, Russia, Congo, South Africa
Artificial diamond : 80 kbar, 1500oC (1) Graphite ⎯⎯⎯⎯⎯⎯⎯→ Diamond (2) Thermal decomposition of methane
15 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
◆ Fullerene, C60 , C70
1985 Discovery of “Buckminsterfullerene”, ‘Bucky ball’
~ Buckminster Fuller(美,1895-1983), an architect, inventor of ‘geodesic’ dome ‘측지선(測地線)’ 돔
Montreal ‘Biosphere’ ★ Nobel Laureates in chemistry (1996) "for their discovery of fullerenes" ◆ Harold W. Kroto ◆ Robert F. Curl, Jr. ◆ Richard E. Smalley (英,1939 ~ ) (美,1933 ~ ) (美,1943 ~ )
Fig. 14.32 Small cluster of fullerite in which ‘Bucky balls’ are packed in a close-packed Structure of C60 : Hexagons and pentagons lattice.
C60: "truncated icosahedron cage",
Æ a polyhedron with 20 hexagonal (6-angled) surfaces and 12 pentagonal (5-angled) surfaces
☺ Sudbury basin (Sudbury meteorite crater), Ontario, Canada
Æ C60 and C70 found (2003)
16 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
BOX 14.1 FRONTIERS OF CHEMISTRY: NANOTUBES, NATURE’S SMALLEST PIPES
First nanotube (1991)
A cluster of carbon nanotubes A strong concentric carbon nanotube. ▶ Carbon nanotube : Æ electrical conductivity vs. diameter Æ capped by bonds to other element or by five-membered rings ▶ Boron nitride (BN) nanotube : Æ weakly semiconducting, independent of diameter Æ capped by W, no five-membered rings 14.17 Silicon, Germanium, Tin, and Lead ◆ Silicon: second most abundant in Earth’s crust 2− ► Minerals: silicates ( SiO3 ), silica (SiO2)
Fig. 14.33 Common forms of silica: (a) Quartz, (b) Quartzite, (c) cristobalite (black parts: obsidian, volcanic rock containing SiO2) ► Preparation: ∆ Reduction of silica by carbon: SiO2 (ss)2+⎯ C() ⎯→+Si(s)2 CO(g)
Chloridation of crude Si : Si(sg) +⎯2 Cl24( ) ⎯→SiCl (l)
Reduction by H2: SiCl42(lg) +⎯2 H ( ) ⎯→+Si(s) 4 HCl(g) ▶ Zone refining
Æ
Fig. 14.34 Zone melting process
17 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14 ◆ Tin
Ore: cassiterite (SnO2)
1200o C SnO22(ss) +⎯C( ) ⎯⎯→Sn(l) +CO (g)
Tin alloys: bronze (Sn/Cu), pewter (Sn/Sb/Cu) ◆ Lead Ore: galena (PbS) ∆ 2 PbS(sg) +⎯3 O22( ) ⎯→+2 PbO(s) 2 SO (g) PbO(ss) +⎯C( ) ⎯→+Pb(s) CO(g)
Passivation by oxide Æ Pipeline of water, Container of H2SO4 Radiation shield
Anti-knocking agent: tetraethyl lead, Pb(CH2CH3)4 Electrode for storage batteries
14.18 Oxides of Carbon
◆ Carbon dioxide, CO2 : anhydride of H2CO3 ⎯⎯→ HC23O(aq)←⎯⎯ CO2(g)+ HO2(l)
BOX 14.2 WHAT HAS THIS HAS TO DO WITH . . . THE ENVIRONMENT?
◈ The Greenhouse Effect
Absorption of IR radiation by CO2(g), H2O(g), CH4(g), N2O(g), O3(g), CFCs Æ Raising the temperature of the Earth Æ Reducing the fossil fuel consumption
An IR absorption spectrum Atmospheric concentration of CO2 (CO2 emission)
◆ Kyoto Protocol to the United Nations Framework Convention on Climate Change (1997)
▶ Other methods:
Æ Removing CO2 by pumping CO2 exhaust into deep sea
Æ Removing CO2 by an aqueous slurry of CaSiO3
2 CO23(gs) ++CaSiO ( ) H2O(l) ⎯⎯→+SiO2(s) Ca(HCO3)2(s)
18 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
Average change of surface temperature of Earth
◆ Carbon monoxide, CO : anhydride of HCOOH, colorless, flammable, almost insoluble, very toxic gas
o 150 C, H24SO HCOOH(aq) ⎯⎯⎯⎯⎯⎯→+CO(g) H2O(l)
− − CO(ga) +⎯OH ( q) ⎯→ HCO2 (aq)
► Formation of metal carbonyls
Fig. 14.35 Bonding of CO to a d-metal atom: (a) Donating a lone pair to form a σ -bond. (Lewis base) * (b) Accepting d-orbital electrons of metal into an empty π -orbital. (Lewis acid)
► Reducing agent:
∆ Fe23O (sg) +⎯3 CO( ) ⎯→+2 Fe(l) 3 CO2(g)
14.19 Oxides of Silicon: The Silicates
Fig. 14.36 Impure silica: amethyst(Fe3+),자수정(紫水晶); agate; onyx. ☺ Amethyst: Birthstone of February, ‘Sincerity and Peace of Mind’
19 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
◆ Silica, SiO2 Æ Strong covalently bonded network structure One Si atom at the center of a tetrahedron of O atoms (each O shared by two Si atoms)
Æ One Si atom + 4 x 1/2 O atoms Æ SiO2
► Quartz(석영,石英) : helical chains of SiO4 units wound around one another ► Cristobalite : obtained by heating quartz at 1500oC, diamond-like structure
O Fig. 14.37 Structure of cristobalite. Si
◆ Metasilicic acid, HS2iO3 and Ortho silicic acid, HS44iO
► Silica gel : obtained by acidifying a solution of sodium orthosilicate (Na4SiO4)
+ 4− 4 H34O(aq)++SiO (aq) x HO2()l ⎯⎯→⋅SiO2(s) xHO2(gel)+6 HO2(l)
– Very high specific surface area (700 m2·g–1) Usage: drying agent, support for catalyst, packing for chromatography column, insulator ► Orthosilicates:
● Zircon, ZrSiO4 : jewelry
● Pyroxene (휘석,輝石) : Chain of SiO4 units (2 corner O atoms shared by neighboring units) 2− Æ Repeating unit is metasilicate ion, SiO3 ; Jade(비취,翡翠), NaAl(SiO3)2
Fig. 14.38 Structure of a mineral, pyroxene. Each tetrahedron is a SiO4 unit. Fig. 14.39 A fibrous mineral, Asbestos
● Tremolite(투각섬석,透角閃石), Ca2Mg5(Si4O11)2(OH)2 Æ Ladderlike structure linked together by chains of silicate units Æ One of the fibrous minerals, asbestos(석면,石綿) Å asbestosis(석면침착증) Æ Withstand extreme heat
● Talc (활석,滑石), Mg3(Si2O5)2(OH)2
Æ sheet like structure formed by SiO4 tetrahedral units Æ soft and slippery 20 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
◆ Aluminosilicates
● Mica(운모,雲母), KMg3(Si3AlO10)(OH)2 Æ Sheets of tetrahedra are held together by extra K+ ions Æ Cleaved into transparent layers, not slippery Æ Used as a furnace window
● Feldspar(장석,長石), KAlSi3O8 Æ aluminosilicate in which half of Si(IV) is replace by Al(III) Æ Major component of granite
Æ Weathered by CO2 and water
2 KAlSi38O (sl) ++2 H2O( ) CO2(g) ⎯⎯→+K2CO3(s) Al2Si2O5(OH)4(s) +4 SiO2(s)
● Granite(화강암,花崗岩) Æ compressed mixture of mica, quartz, and feldspar
Fig. 14.40 A transparent aluminosilica, Mica, with high m.p. Fig. 14.41 Graphite ◆ Silicones Æ Synthetic materials consisted of long –O–Si–O–Si– chains with organic sidegroups Æ Waterproof fabrics
Fig. 14.42 A typical structure of silicone. (cf. Fig. 14.38 of purely inorganic pyroxene.)
21 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
14.20 Other Important Group 14/IV Compounds ◆ Carbides(탄화물,炭化物): monatomic or polyatomic anions of carbon ► Saline carbide Æ methide, C4− carbide Å strong Brønsted base
Al43C (sl) +⎯12 H2O( ) ⎯→+4 Al(OH)3(s) 3 CH4(g)
2− Æ acetylide, C2 carbide
CaC22(sl) +⎯2 H O( ) ⎯→Ca(OH)2(s) +C2H2(g) ► Covalent carbide ● Carborundum, SiC
o SiO (ss) +⎯3 C( ) 2000⎯⎯C→4 SiC(s) +2 CO(g) 2 Fig. 14.43 Carborundum crystals. ► Interstitial carbide Æ Formed by direct reaction of a d-metal with carbon above 2000oC Æ C atoms in interstices held metal atoms together, very hard material with m.p. above 3000oC ● Tungsten carbide, WC Æ cutting surfaces of drills
● Iron carbide, Fe3C Æ important component of steel
◆ Tetrachlorides (사염화물,四鹽化物)
650o C CH42(gg) +⎯4 Cl ( ) ⎯⎯→+CCl4(g,l when cooled) 4 HCl(g)
SiCl42(ll) +⎯2 H O( ) ⎯→+SiO2(s) 4 HCl(aq) ◆ Cyanides
1100o C, Pt 2 CH43()gg+ 2 NH()+ 3 O2(g)⎯⎯⎯⎯→2 HCN(g)+6 H2O()g
◆ Silanes : compounds of silicon with hydrogen
SiCl44+⎯ LiAlH ⎯→+SiH4LiCl +AlCl3
OH− SiH42(gl)2+⎯ HO() ⎯⎯→+SiO2(s)4 H2(g)
THE IMPACT ON MATERIALS 14.21 Glasses An ionic solid with amorphous network structure. o Heating Silica (SiO2) and metal oxides (MO) over 1600 C −−Si O −Si − ⎯⎯→− Si −O−+−M ► Optical fiber: Made by drawing a thin fiber from an optically pure glass rod heated until it softens.
Fig. 14.44 Glass fibers.
22 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 14
► Soda-lime glass: 12% Na2O(soda) + 12% CaO (lime)
► Borosilicate glass: addition of 16% B2O3 Æ pyrex
▶ Reactions of glass:
2− + With HF: SiO26(sa) +⎯6 HF( q) ⎯→+SiF (aq) 2 H3O (aq)
1400o C With a strong alkali: SiO22(sl) +⎯Na CO3( ) ⎯⎯→+Na 2SiO3(s) CO2(g)
14.22 Ceramics
Fig. 14.45 Layers of clay particles Fig. 14.46 A synthetic solid foam, aerogel.
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