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 15

CHAPTER 15 THE ELEMENTS: THE LAST FOUR MAIN GROUPS

GROUP 15/V : THE NITROGEN FAMILY

Electronic configuration: ns23np Oxidation states: –3 ~ +5 Different reactivities

Stable N2 Burning in air, P Semiconductor, As, Sb Metal, Bi

Fig. 15.1 N2(l), Sb, red P, Bi, As

15.1 The Group 15/V Elements

◆ Nitrogen, N o o o m.p.: N2(–196 C) cf. O2(–183 C), Ar(–186 C) Stable triple bond: N≡ N, 944 kJ·mol–1

Bacterial fixation of N2 in nodules on the roots of beans, alfalfa,… Haber-Bosch process Electronegativity: 3.0 – Multiple oxidation states: NH3(–3), HNO3(+5), N3 (azide,–1/3) Fig. 15.2 The pea-plant bacteria. Small atomic radius: π -bond formation from 2p-orbitals, N2O3 ◆ Phosphorus (인,燐), P

Large atomic radius Æ π -bond formation from 3p-orbitals Æ single bonds, P4O6

1 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

Mineral, apatites, Ca3(PO4)2

∆ 2 Ca34(PO )2(ss) ++6 SiO2( ) 10 C(s) ⎯⎯→+P4(g) 6 CaSiO3(l) +10 CO(g)

White (or Yellow) phosphorus: soft, white, very reactive (burns in air, stored in water),

tetrahedral P4 molecules, chemiluminescence (trioxide of phosphorus), 연막탄

Red phosphorus: less reactive, matches, amorphous network (chains of linked P4 tetrahedra) Obtained by heating (240oC) white phosphorus without air (iodine catalyst)

Red phosphorus, powder ◆ Arsenic (비소,砒素), As Metalloid GaAs Æ used in lasers in CD players ◆ Antimony, Sb Metalloid Pb/Sb electrodes in lead storage batteries Semiconductors (diodes) ◆ Bismuth, Bi Fig. 15.3 Minerals: Orpiment(웅황,雄黃, As2S3), Stibnite Metal (휘안광,輝安鑛,Sb2S3), Realgar(계관석,鷄冠石,As4S4) Low m.p. (271.5oC) Low melting alloys with Pb, Cd… Æ Activating sprinklers in fire detector

15.2 Compounds with Hydrogen and the Halogens

▶ Ammonia, NH3 Dipole moment: 1.47 D (cf. water: 1.85 D) Poor solvent for strong ionic salts ex. KCl Good solvent for ionic salts with polarizable anions ex. KI

Very soluble in water: hydrogen bonds between NH3 and H2O Autoprotolysis:

⎯⎯→ + − 2 NH34(am)←⎯⎯ NH (am) + NH2(am) ,

+ − −33 o Kam =[NH4 ][NH2 ] =1×10 at –35 C

Strong Lewis base:

2+ 2+ 2+ Fig. 15.4 Add NH3 to Cu (aq) Cu()aq +⎯4 NH33()aq ⎯→Cu(NH)4()aq

2 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ▶ Ammonimum salts Used as fertilizers Decomposition:

∆ (NH42)CO3(sg)⎯⎯→+2 NH3() CO2()g+H2O()g

Oxidation:

250o C NH43NO(sg)⎯⎯⎯→+NO2( ) 2 HO2(g)

< 300o C 2 NH43NO (sg) ⎯⎯⎯⎯→+2 N2( ) O2(g) +4 H2O(g) Å explosive (dynamite)

▶ Hydrazine, N2H4 Oily, colorless liquid Used as a rocket fuel Obtained by slow oxidation by hypochlorite:

−−aqueous alkali 2 NH32(aq) + ClO (aq) ⎯⎯⎯⎯⎯→+N H4(aq) Cl (aq) +H2O(l)

Removing corrosive oxygen from water in high T & P steam furnace

NH24(aq)+⎯O(2g) ⎯→+N2(g) 2 H2O(l)

▶ Nitrogen halides, +3 oxidation state

NF3 (most stable), NCl3 (reacts with water), NI3·NH3 (explosive)

▶ Nitrides, N3–

∆ 3 Mg()sg+⎯N23( ) ⎯→ MgN2(s)

Mg32N (sl) +⎯6 H2O( ) ⎯→+3 Mg(OH)2(s) 2 NH3(g) Fig. 15.5 Magnesium nitride, Mg3N2

– ▶ Azides, N3

175o C N22O(gl) +⎯2 NaNH ( ) ⎯⎯→+NaN3(s) NaOH(l) +NH3(g)

● NaN3 : shock-sensitive, used in airbags for automobiles

2 NaN32(ss) ⎯⎯→+2 Na( ) 3 N (g)

● Hydrazoic acid, HN3

⎯⎯→ + − HN32+H O←⎯⎯ H3O +N3, pKa = 4.6

3 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

▶ Phosphine (IUPAC name, Phosphane), PH3 Poison gas

Used as fumigants (훈증약, 燻蒸藥) Å pesticides Preparation:

3−−3– 2 P (sl) +⎯6 H23O( ) ⎯→+2 PH (g) 6 OH (aq), ( phosphide ion: P )

▶ Phosphorus halides

● Phosphorus trichloride, PCl3 Liquid, pesticides, oil additive, flame retardant

P42 + 6 Cl ⎯⎯→ 4 PCl3

● Phosphorus pentachloride, PCl5 Colorless, water-sensitive solid, chlorinating reagent

PCl32 + Cl ⎯⎯→ PCl5

Hydrolysis Æ no change in oxidation states:

+33+ PCl32(ll)3+⎯ HO() ⎯→H3 PO3(s)3+ HCl(g)

+55+ PCl52(ll)+⎯4 H O( ) ⎯→+H3 PO4 (s) 5 HCl(g)

15.3 Nitrogen Oxides and Oxoacids

Nitrogen oxides, NOx : “nox” Å air pollutants

▶ Dinitrogen oxide (Nitrous oxide, “laughing gas”), N2O +1

250o C NH43NO(sg)⎯⎯⎯→+NO2( ) 2 HO2(g)

Tasteless, unreactive, nontoxic gas Used as an anesthetic, foaming agent for whipped cream

4 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ▶ Nitrogen oxide, NO +2 Colorless gas NO gas from exhausts of planes, cars Æ acid rain Neurotransmitter Æ dilating blood vessels Preparations:

1000o C, Pt 4 NH32(gg) +⎯5 O ( ) ⎯⎯⎯→+4 NO(g) 6 H2O(g)

− −+ 2 NO2 (aq) ++2 I (aq) 4 H (aq) ⎯⎯→+2 NO(g) I22(aq) +2 H O(l)

Acid rains:

2 NO()gg+⎯O22() ⎯→2 NO()g

3 NO22(gl) +⎯H O( ) ⎯→+2 HNO3(aq) NO(g)

▶ Nitrogen dioxide, NO2 +4 Choking, poisonous brown gas

⎯⎯→ 2 NO2 (brown)←⎯⎯ N24O (colorless)

Disproportionation (불균등화 반응):

+4 +5 +2 NO2 (gl)+⎯H2O( ) ⎯→+2 HNO3(aq) NO(g)

Smog formation

▶ Dinitrogen trioxide, N2O3 +3 Blue gas, anhydride of nitrous acid

NO(23gl)+⎯H2O() ⎯→ 2 HNO2(aq) Fig. 15.6 Dinitrogen trioxide, N2O3 −100o C – Deep blue liquid Pale blue solid ▶ Nitrites, NO2 +3 ⎯⎯⎯⎯→ Obtained by reducing nitrates:

350o C KNO32(ss) +⎯Pb( ) ⎯⎯→+KNO (s) PbO(s)

Processing meat products: Retarding bacterial growth Forming a pink complex with hemoglobin Æ inhibits oxidation of blood (brown)

▶ Nitric acid, HNO3 +5 Colorless liquid acid, b.p. 85oC Used as fertilizers and explosives Å nitroglycerin (dynamite) > trinitrotoluene (TNT) Preparation: Three-step Ostwald process Step 1: Oxidation of ammonia

−3 +2 850oC, 5 atm, Pt/Rh 4 HN3()gg+5 O2 ()⎯⎯⎯⎯⎯⎯→+4NO()g6 H2O()g

5 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 Step 2: Oxidation of NO

+24+

2 NO(gg)+⎯O2 ( ) ⎯→2NO2 (g)

Step 3: Disproportionation in water

+4+5+2 3 N O2 (gl) +⎯H23O( ) ⎯→+2 H N O (aq) N O(g)

15.4 Phosphorus Oxides and Oxoacids

▶ Phosphorous(III) oxide, P4O6

P42(sg, white) +⎯3 O ( ) ⎯→ P4O6(s) Å anhydride of phosphorus acid

▶ Phosphorous acid, H3PO3

P46O(sl)+⎯6 HO2() ⎯→4 HP3O(3aq) Å diprotic acid !

▶ Phosphorous(V) oxide, P4O10

P42(sg, white) +⎯5 O ( ) ⎯→ P4O10(s) Å drying agent, anhydride of phosphoric acid

▶ Phosphoric acid, H3PO4

P41O0(sl)+⎯6 HO2() ⎯→4 HP3O4(aq)

● Usage of phosphoric acid:

Fertilizers, food additives, detergents

▶ Phosphates Ca(PO)()sl+⎯2 HSO() ⎯→+2 CaSO()sCa(HPO)(s) 342 24  4 242 superphosphate

● Condensation reaction (축합반응,縮合反應) :

Pyrophosphoric acid (H4P2O7)

6 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ● Polyphosphates ★ ATP (Adenosine triphosphate): Energy source in cells

– o ATP + H2O ⎯⎯→ ADP (Adenosine diphosphate) + H2PO4 , ∆=G −30 kJ at pH 7

GROUP 16/VI : THE OXYGEN FAMILY 15.5 The Group 16/VI Elements Electronic configuration: ns24np Chalcogens (ore former), 칼코젠 Etymology(어원,語原): Greek chalkos (ore) + -gen (former); from the occurrence of oxygen and sulfur in many ores cf. Halogen (salt former): Greek halos (salt)

7 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ▶ Oxygen, Most abundant element in Earth’s crust Much more reactive than nitrogen

Gas: O2 Colorless, tasteless, odorless gas Pale-blue liquid at -183oC Paramagnetic (two unpaired electrons) Heavily consumed in steel industry Responsible for combustion

Used in medicine, welding Fig. 15.7 Pale blue liquid O2.

▶ Ozone, O3 Blue gas with pungent smell Condenses at -112oC to an explosive blue liquid

Prepared by passing electric discharge through O2 Also present in smog: UV NO2 ⎯⎯→ NO + O

OO+⎯⎯→O 23

Presence of ozone in stratosphere vital to lives on Earth Fig. 15.8 Dark blue liquid O3.

Fig. 15.9 Elecronegativities. Fig. 15.10 Radii (in pm) of atoms and anions of Group 16/VI elements.

▶ Sulfur Atomic radius: S > O EN & IE: S < O

Polarity: S-H < O-H Æ H2S(g), H2O(l) ∆, 200o C Catenation (사슬화 반응) Æ S8 rings ⎯⎯⎯⎯→ long strands of “plastic sulfur” Disulfide link: – S – S – Æ structure of proteins Ores:

8 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

Fig. 15.11 Sulfide ores: PbS (galena,방연광,方鉛鑛), HgS (cinnabar,진사,辰沙)

FeS2 (pyrite,황철광,黃鐵鑛), ZnS (sphalerite,섬아연광,閃亞鉛鑛)

► Frasch process: Extraction of elemental sulfur in porous limestones in salt domes Steam injection Æ Liquefying sulfur (m.p. 115oC) Æ Pumped out by compressed air ► Claus process:

2 H22S()gg+⎯3 O() ⎯→2 SO2()g+2 H2O(l)

o 300 C, Al23O 2 H22S()gg+SO()⎯⎯⎯⎯⎯→+3 S(l) 2 H2O()g

● Elemental sulfur

Yellow, tasteless, odorless, insoluble, nonmetallic molecular solid, S8 rings

Fig. 15.12 Common crystal forms of sulfur: (a) blocklike stable rhombic form (b) needlelike monoclinic form

● Selenium, Se nonmetal, conductivity increases by exposure to light, used in solar cells ● Tellurium, Te Metalloid, semiconductor, alloys ● Polonium, Po

radioactive metalloid, source of α -particles, used in antistatic devices in textile industry Fig. 15.13 Se(nonmetal) & Te(metalloid). 15.6 Compounds with Hydrogen

▶ Water, H2O ★ Drinking water

Aerator: removing H2S, oxidizing organic compounds to CO2, adding O2 2+ 3+ 2+ Lime, Ca(OH)2: pH increase, precipitates hydroxides of Mg , Fe , Cu Å softening water

Primary settling basin: Addition of coagulants: Fe2(SO4)3 or alum, Al2(SO4)3·18H2O Æ Coagulation (응집,凝集) and flocculation (엉김) of precipitates

9 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ● Coagulation: irreversible aggregation of small particles into larger particles ● Flocculation: reversible, loose aggregation of somewhat larger particles to form a fluffy gel

Addition of CO2: lowering pH, promoting ppt of Al(OH)3

Secondary settling basis: adsorbing CaCO3, bacteria, dirt, algae Sludge lagoon: combining ppts from both settling basins into sludges for disposal Sand Filter, Activated charcoal pH adjustment

Chlorination: 1g Cl2 per 1000 kg water +− Cl22(g) +⎯2 H O(l) ⎯→+H3O (aq) Cl ()aq +HClO(aq)

Fig. 15.14 Typical steps in the purification of drinking water. Water as an oxidizing agent −− 2 H22O(l) +⎯2 e ⎯→2 OH (aq) +H (g) , E = −=0.42 V at pH 7

2 Na(sl) +⎯2 H22O( ) ⎯→+2 NaOH(aq) H (g) Water as a mild reducing agent: +− 4 H (aq) ++O22(g) 4 e ⎯⎯→2 H O(l) , E = +=0.82 V at pH 7 3+ Water as a Lewis base: Forming complexes, Fe(H2O)6 , hydrolysis

▶ Hydrogen peroxide, H2O2 Very pale blue liquid denser than water m.p. –0.4oC , b.p. 152oC

Weak acid (pKa=11.75) Stronger oxidant than water

3% aqueous solution of H2O2: mild antiseptic

On contact with blood, 2 HO22(aq)⎯⎯→+2 HO2(l) O2(g)

▶ H2E : binary compounds with hydrogen E: Group 16/VI elements except O Toxic gases with offensive odors Insidious poison paralyzing olfactory(후각,嗅覺) nerve ends

▶ H2S Smell of a rotten egg Pale green discoloration due to a deposit of FeS

10 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 Preparation:

FeS(sa)2+⎯ HCl(q) ⎯→+FeCl22(aq)HS(g)

Hydrosulfuric acid: aqueous solution of H2S, diprotic weak acid

+− H22S()aq +⎯HO(l) ⎯→+H3O()aq HS()aq

−+2− HS (aq) +⎯H23O(l) ⎯→+H O (aq) S (aq)

▶ Polysulfane: Sulfur analog of hydrogen peroxide

Catenated molecular compound, HS – Sn – SH (0

15.7 Sulfur Oxides and Oxoacids

SOx : “sox”

▶ Sulfur dioxide, SO2 Colorless, choking, poisonous gas Volcanic eruption, decomposition of vegetation Oil and coal combustions

Oxidation of hydrogen sulfide:

2 H22S()gg+⎯3 O() ⎯→2 SO2()g+2 H2O(l) Anhydride of sulfurous acid:

SO22(gl) +⎯H O( ) ⎯→ H2SO3(aq)

Æ Equilibrium mixture of two molecules

Æ Forming “clathrates”, SO2·xH2O ‘a molecule trapped in a cage of other molecules’

▶ Sulfur trioxide, SO3

2 SO22(gg) +⎯O ( ) ⎯→ 2 SO3(g)

Æ Forming trimers, S3O9

▶ Sulfuric acid, H2SO4 Colorless, corrosive, oily liquid (b.p.300oC) Strong hydrogen bonds with water Strong Brønsted acid: First deprotonation – Second deprotonation, HSO4 , weak acid Oxidizing agent (Fig.15.16)

Dehydrating agent (Fig.15.17) Fig. 15.16 Oxidation of NaBr by conc H2SO4. Br2(g) ↑ CH12 22O(11 ss)⎯⎯→+12 C() 11 H2O(l)

11 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

Fig. 15.17 Dehydrating of sucrose by concentrated H2SO4.

Production of H2SO4 : ► Contact process (접촉법,接觸法)

1000oC S(sg)+⎯O22() ⎯⎯→SO()g

o 500 C,V25O 2 SO22(gg) +⎯O ( ) ⎯⎯⎯→2 SO3(g)

SO32(gl) +⎯H SO4( ) ⎯→ HS22O7(l) Å Oleum (발연황산,發煙黃酸)

HS22O7(ll)+⎯H2O() ⎯→ 2 HS2O4(l)

15.8 Sulfur Halides No reaction of sulfur with iodine

▶ Sulfur hexafluoride, SF6 Obtained by spontaneous ignition of sulfur in fluorine Dense, colorless, odorless, nontoxic, insoluble gas Very high IE Æ good gas-phase electrical insulator

▶ Disulfur dichloride, S2Cl2

Yellow liquid, nauseating smell Used in vulcanizing(가황반응,加黃反應) rubber

▶ Sulfur dichloride, SCl2 Å red liquid, foul odor

FeCl3 S2Cl2 + Cl2 ⎯⎯⎯→ 2 SCl2

SCl2 + 2 C2H4 ⎯⎯→ (ClCH2CH2)2S poisonous ‘mustard(겨자) gas’

GROUP 17/VII : THE HALOGENS

Electronic configuration: ns25np

Forming diatomic molecules, X2 Oxidation states: –1 ~ +7

Fig. 15.18 Electronegativites of halogens.

12 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

Fig. 15.19 Radii (in pm) of atoms and anions of halogens.

15.9 The Group 17/VII Elements

▶ Fluorine, F, F2 Most abundant halogen on Earth’s crust

Ores: fluorspar(형석螢石,CaF2), cryolite(빙정석氷晶石,Na3AlF6), fluorapatite(인회석燐灰石,Ca5(PO4)3F) Strongest oxidizing power (Eo = +2.87 V) Highest EN Æ +1 oxidation number in all compounds

F2 gas Æ Used in making UF6, SF6 F– ion: small size, large lattice energy, less soluble Æ remains on Earth’s crust

▶ Chlorine, Cl, Cl2 Electrolysis of rock salt or brine o Cl2 : pale yellow-green gas, b.p. –34 C Reactions:

2 Fe(sg) +⎯3 Cl23( ) ⎯→ 2 FeCl (s) −− 2 Br (aq) +⎯Cl22(g) ⎯→+Br (l) 2 Cl (aq)

▶ Bromine, Br, Br2 Br : Brown, fuming liquid, m.p. 27oC, b.p.59oC 2

Organic bromides: fire retardant in textiles, pesticides, Fig. 15.20 Reaction of Fe with Cl2. photographic emulsion

13 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

▶ Iodine, I, I2 Purple-black nonmetallic solid (m.p. 114oC) 2000 kg seaweed Æ 1 kg iodine I– ions in brine from oil well

−−o 2 I (aq) +⎯Cl22(g) ⎯→+I (aq) 2 Cl (aq) , ∆=G −54.54 kJ

– I3 (aq): brown Mild oxidizing antiseptic: when dissolved in alcohol

Fig. 15.21 Solutions of I2 in (1) CCl4, (2) H2O, (3) KI(aq), (4) KI(aq) + starch ▶ Astatine, At Radioactive Obtained by bombarding Bi with α − particles in cyclotron

15.10 Compounds of the Halogens

▶ Interhalogen compounds:

XX’, XX’3, XX’5, XX’7 (X is heavier than X’)

Cl22(gg) +⎯3 F ( ) ⎯→ 2 ClF3(g)

Cl22(gg) +⎯5 F ( ) ⎯→ 2 ClF5(g)

▶ Hydrogen halide, HX Æ Gases except HF (liquid below 20oC)

H22(gg)+⎯X() ⎯→2 HX(g) Å Explosive for F2

CaF22(sa) +⎯2 H SO4( q,conc) ⎯→Ca(HSO4)2(aq) +2 HF(g) Å Safe & slow

∆ KI(sa)+⎯H34PO(q) ⎯→+KH2PO(4aq) HI(g)

☻ Hydrogen fluoride (HF) : Used in making …

● Teflon (polytetrafluoroethylene) Å relatively inert material

● R134a (CF3CH2F) Å safe refrigerant ( CFC )

14 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

☻ Hydrofluoric acid (HF) + NH4F Æ Frosting glass (lamp bulb) and silica

Fig. 15.22 Mixture of HF & NH4F reacts with glass. ◆ Halogen oxoacids

▶ Hypohalous acid, HXO

0+1−1

Cl22(g)+⎯H O(l) ⎯→HClO(aq)+HCl(aq) Å disproportionation reaction

0+1−1 −−− – Cl2 (ga) +⎯2 OH ( q) ⎯→+ClO (aq) Cl (aq) +H2O(l) Å producing hypohalite (XO )

+− 2 HClO(aq) ⎯⎯→+2 H (aq) 2 Cl (aq) +O2 (g) Å action of household bleach

– ▶ Chloric acid, HClO3 and Chlorate ion, ClO3

−−∆ − 3 Cl23(ga) +⎯6 OH ( q) ⎯→+ClO (aq) 5 Cl (aq) +3 H2O(l)

∆ 4 KClO34(ss) ⎯⎯→+3 KClO ( ) KCl(s)

∆, MnO2 2 KClO3(s) ⎯⎯⎯⎯→2 KCl(s) +3 O2(g) Å Laboratory source of O2 gas

▶ Chlorine dioxide, ClO2 Paramagnetic, yellow gas Used in bleaching paper pulp Obtained by reducing chlorate:

2 NaClO32(aq) ++SO (g) H2SO4(aq,dilute)

⎯⎯→+2 NaHSO42(aq) 2 ClO (g) – ▶ Perchloric acid, HClO4 and perchlorate ion ClO4

−−+ − ClO32(aq) +⎯H O(l) ⎯→+ClO4(aq) 2 H (aq) +2 e

☻ Solid propellant of booster rockets of space shuttles:

Fe23O 3 NH 44ClO (ss) +⎯3 Al( ) ⎯⎯→

Al23O (ss) + AlCl3( ) +6 H2O(g) +3 NO(g)

Fig. 15.23 White smoke, Al2O3 + AlCl3

15 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

GROUP 18/VIII : THE NOBLE GASES Electronic configuration: ns26np Closed-shell structure Monatomic gases 1% in atmosphere Obtained by fractional distillation of liquid air except He, Rn No longer noble after 1962

Æ XePtF6 (Neil Bartlett), KrF2

15.11 The Group 18/VIII Elements ▶ Helium, He Second largest abundance in the universe after hydrogen A component of natural gases trapped under rock Æ Collected as a result of α emission of radioactive elements α − particle : a helium-4 nucleus, 42He + Nonflammable Æ used in blimps (비행선飛行船) b.p. 4.2 K Æ used in NMR spectrometer No solid phase under ordinary pressures

Useful for study of gryogenics(저온학低溫學)

Helium-II Å superfluid (초유체超流體)! ▶ Neon, Ne Emits orange-red color when electric current flows through it. Æ Neon signs ▶ Argon, Ar Provides inert atmosphere for welding Fig. 15.24 Phase diagram of He-4. Light bulbs Å conducting heat away from filament

16 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

Fig. 15.25 Fluorescent lightings: Ne(red), Ne+Ar(blue-green), Glass coated with phosphor(인광물질)(yellow). ▶ Krypton, Kr Intense white light when electric discharge is passed through it Æ Airport runway lighting Atmospheric Kr level Æ indication of nuclear activity ▶ Xenon, Xe Used in halogen lamps for automobiles Used in high-speed photographic flash tubes ▶ Radon, Rn Radioactive Radon hot springs in Misasa, Japan

15.12 Compounds of the Noble Gases

–1 Fig. 15.26 Ionization energies (in kJ·mol )of noble gases. Fig. 15.27 Crystals of XeF4.

▶ Xenon fluorides: XeF2, XeF4, XeF6 Reactions:

Pt(ss) +⎯XeF44( ) ⎯→+Xe(g) PtF (s) Å fluorination

6 XeF42(s) +⎯12 H O(l) ⎯→+2 XeO3(aq) 4 Xe(g) +3 O2(g) +24 HF(aq) Å hydrolysis

Xenon trioxide, XeO3 Æ anhydride of xenic acid, H2XeO4

alkali – disproportionation 4– H2XeO4 ⎯⎯⎯→ hydrogen xenate ion, HXeO4 ⎯⎯⎯⎯⎯⎯→ Xe + XeO6 (perxenate) sulfuric acid Ba2XeO6 ⎯⎯⎯⎯→ XeO4(g) Å explosively unstable gas

17 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

THE IMPACT ON MATERIALS 15.13 Luminescent Materials ▶ Incandescence(백열白熱): light emitted by a hot body ex: filament ▶ Luminescence(발광發光): emission of light by a process other than incandescence ► Chemiluminescence: emission of light by products formed in energetically excited states in a chemical reaction

☻ Perylene, C20H12, emitting blue fluorescence, used as a blue-emitting dopant material in OLEDs

Perylene Fig. 15.28 Chemiluminescence of perylene upon addition of H2O2.

► Bioluminescence: a form of chemiluminescence generated by a living organism

☻ Firefly luciferin

▶ Fluorescence(형광螢光): emission of light from molecules excited by radiation of higher frequency ▶ Phosphorescence(인광燐光): emission of light from a molecule that remains excited state after the stimulus Has ceased ▶ Triboluminescence(마찰발광): luminescence resulting from mechanical shock to a crystal

▶ Phosphor(인광체燐光體) CRT TV screen

Red phosphor: yttrium oxysulfide, Y2O2S activated by Eu Blue phosphor: ZnS activated by Ag Green phosphor: ZnS activated by Cu ▶ Biotracer: ex. Fluorescein: a fluorescent dye molecule attached to protein molecules

18 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15

▶ Scintillation counter: detecting radioactivity which triggers fluorescence from a sensor (phosphor) 15.14 Nanomaterials 1 ~ 100 nm size particles

Fig. 15.29 Micrographs of the crystallization of a block copolymer. (a) Natural (b) Nanotech.

Fig. 15.30 Constructing a ring of Fe atoms on Cu. Fig. 15.31 Forest of carbon nanotubes.

“Top-down” lithography (석판인쇄술) “Bottom-up” self-assembly

BOX 15.1 FRONTIERS OF CHEMISTRY: SELF-ASSEMBLING MATERIALS

◈ Self-assembly

▶ Static self-assembly: stable structure, irreversible

Ex: Folding of polypeptide chains into proteins, Formation of the double helix of DNA

19 2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 15 ▶ Dynamic self-assembly: involves interactions that dissipate energy, reversible ▷ Oscillating reactions: Belousov-Zhabotinskii reaction

▷ Convection patterns ▷ Coordinated motions of fishes and migrating birds ▷ “Smart gel” Æ Four types of forces responsible for the adaptive behavior of “smart gel”

Ionic region Nonpolar hydrophobic region (attraction or repulsion) (excluding water)

Hydrogen bonds Dipole-dipole interaction

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