Note for CHM 218 with Professor Berger at IPFW
Note for CHM 218 with Professor Berger at IPFW
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Date Created: 02/06/15
141 31131112 14 e The many 14 Elements Ehnnnt mntc hue Group 14 eonststs of anonrmetal C two semkmetals st and Ge and two weak meta1s sn and Pb c st and Ge have htgn melting C WW m potnts charactmsn ofnonmetals andsemtmeta1s wtth eova1ent st mu mu netwotk bondng The meta1s have famy 1ow memng potnts but long at m asst htttttd ranges All othe e1ements eatenate form ehatns of atoms wtth hemse1vesbtttthe abt1tty to eatenate deeteases down the goup c in 232 2523 gtgt st gt Ge a 5n gtgt Pb Pb 27 I751 Multiple otndatton states oeettt for a11the e1ements All ofthem enhtbttthe4 otndatton state whteh tnvo1ves eova1ent bondng even for the two meta1s The fttst thtee e1ements enhtbtt the 41 oxxdahon state Ttn and1ead a1so enhtbttthe 2 oxxdahon state merbpalr effect Carth Thtee allotxopes ofcarbon are known Allotxopes are two otmotephysteany dtsttnetfotms of an e1ement tn a smgle phase The allotxopes of carbon ate dtamond gaphxte and fulla enes Diammtd 1n the dtamond form of eabon there ts a netwotk of smgle tetrahedrally mnged eova1entbonds Dtamond ts an e1eetnea1 tnstdatot but at exeeuentthetma1 eondtetot becauseofxtsstxucture Beeattsethegtant mo1eett1e ts heldtogether by a continuous netwotk of eova1entbonds1ttt1e movement oftndvtdta1 eatbon atoms ean oeettt Henee any added heat energy wtu be transferred as mo1eett1at motion dtteetTy attoss the who1e damond Dtamondtsasohdto ova 400mg beeause an enormous amount of snargyxs needed to breakdusse strong Figure142 Structure o1 dlamond eova1entbonds Tn notma1 damond the anangement othe tetrahedraxs the same as that tn the eubte ZnSasphaleme tonte stxucture FCC anay of c atoms wtth c atoms tn 12 ofthe tetrahedral holes Thetets a1so at Extremely tae formlonsdalate named attetthe crystallogapher KathlemLonsdale tn whteh the tetrahedra ate anangedm the hexagonal Znsrwunzlte structure 142 The denstty of damond 5 g em39z ts mueh greate than that ofgraphtte 2 2 g em39z LeChateher39s Pnnetpte suggests that damondformauon from gaphxte ts favoredunder eonduons ofhtgn pressure Furthemore to overeome the eonstderabte aeuvauon enegy barner aeeompanytng the rearrangement of eova1ent bonds htgh temperatures a1so are requtred The See enegy of damondts 2 9 k1 motquot htghe than that ofgraphxte Tt ts on1y the very slow hneues ofthe proeess that prevents dtarnonds from erumbhng tnto gtaphtte Graphite Graphtte eonststs oflayers ofcarbon atoms wtthtn the1ayers eova1ent bonds hold the earbon atomstn slxrmemberednngs The Barbour earbon bond1ength tn gaphxte ts 141 pm These bonds are mueh shorterthan thosetn damond 154 pm but very stmt1arto the 140 pm bonds tn benzene cth suggesung mutupte bondng between the earbon atoms wtthtn the 1ayers Ltke benzene r4 4 gaphxte ts assumed to have a de1oea1tzed 7E e1eetron 5 system througnout the plane of the earbon nngs resu1ung eom ovenap ofthe 2b orbtta1s at nght 7 ang1esto thep1ane ofthenngs Thts arrangement wou1dresu1t tn a net 1e bonds between eaeh patr of earbon atoms The measuredbond1engthts eonststent wtth thts assumpuon r Er The dtstanee between the earbon 1ayers ts very 1arge 335 pm andts more than twtee the va1ue ofthevan dr Waals radtus of a earbon atom Henee the atuaeuon between 1ayers ts very weak In the eommon hexagonal form ofgaphtte a1temaung1ayers are abgned to gve an abab arrangement Lookmg atthe sequenua11ayersonerha1 ofthe earbon atoms are 1oeatedm 1tne wtth earbon atoms tn the p1anes above and be1ow and the otherhatf are 1oeated above and be1ow the eenters of the nngs Figure 143 structure at grapmte The 1ayered strueture and de1oea1tzed e1eetrons of graphtte aeeount for one oftts most tnteresung properuestts abt1tty to eonduet e1eetrtety More speci cally the eondteuvtty tn the plane ofthe sheets ts about 5000 umes greaterthan that at ngnt ang1es to the sheets Graphtte ts a1so an ereeuent 1ubneant by vtrtue of the abthty of sheets of earbon atoms to shde over one another However thts ts not qutte the who1e story Graphtte a1so adsorbs gas mo1eeu1es between tts 1ayers Thus many ehemtsts argue that the gaphxte sheets are ghdng on mo1eeu1ar ball beanngs narne1y the adsorbed gas mo1eeu1es 143 Even tlnougn gaphlte ls tlnemodynamleally more stable than darnond rt ls lnneueally more reaeuye as aresult of tlne separauon of tlne earbon slneets A wlde range of substanees from alkall metals tlnrougn tlne halogens to metal hallde eompounds are known to reaet wltln gaphlte In tlne resulung produets tlne graplnte strueture ls essenually preseryed wltln tlne lntrudng atoms or lons mung between tne layers m afarly stolelnometne rauo Fullerenes Fullerenes eonsutute a famlly of struetures ln wlneln me carbon atoms are mange a when or rtnnretu slmnurs of huckmlnsle ullerene cm elhpsmdal strueture To make suen astrueture tlne earbon atoms form we and slxrmemba39ednngs slmtlarto tlne pattern ofllnes on a soeeer ball the early name for crn was soeeerane The 607 member allotrope cm buelrmlnsterfullerene ls tlne easlest to prepare andls splneneal The 707 member allotrope qquot ls tlne nert most eommonly ayarlable fullerene wltln an alllpsmdal strueture Eyennumbered fullerenes from an to well over cnn are known on lsLhe smallest stablefullerene altlnougln a great degree ofbond stram cm ls tlne most reaeuye of tlne fullerenes and deeomposes ln an one metlnod ofmanufactunng tlne fullerenes ls to use an lntense laser beam to lneat graplute to temperatures of over 10 000 C Attlnese temperatures seeuons oftlnelnexagonal planes ofcarbon atoms peel ofthe surface andwrap tlnemselyeslnto balls Common soot eontams fullerenes andtlney have been found ln naturally oeeumng gaphlte deposlts Some astroelnemlsts argue tlnattlnese moleeules emst extenslyely ln lnterstellar mare Dlamond andgrapnlte are lnsoluble ln all solyents beeause they have eoyalent struetures The fullerenes naye eoyalentbonds wltlun tlne umts but only dsperslon forces lnoldtlne umts togetlner ln tlne solldphase As a result they are very soluble ln nonpolar solyents suen as hexane and toluene Altlnougn blackln tlne solld plnase fullerenes drmlay awlde range of eolorsln soluuon crn gyes anlntensemagentarpurple eolor qquot ls wlne red and qr ls bnghtyellowrgreen cm lsgolden yellow All thefullerenes subllmewhen lneated a property proyldrng further eyldenee of tlne wealrlntemoleeular forces crn moleeulespaelrtogetlnerln tlne same way metal atoms doformlng afacercentered cublc arrangement The fullerenes have low densmes about 1 5 g em and they are noneonduetors of elecmnty 144 The nhermslry nfthesennvel muleeules ls sull a eld nflmanseresearnh The fullerenes ae easlly reduced u man by mamuh wuh Grnup l ald Grnup z me als Fm Example luhdlum ts wnhlh he mhasuees lu he c5n lamce u gve Rbgcm Thls Enmpnundls a suueeemduem a emuelauues 28 K heeause l s structure ls a ually Rh HcmZ The ma elemhs assnnaeed wuh he fullermes ae ee u mnve hmugmm he uys al lus llke huse m ame al As he eamues lu he llleumes ae qul e large l ls pusslhle u m ame al lm wuhlu he mature An Example unhls ls Lang where he syman ls used u Indicate that he 3 me al lm ls wnhlu he Mla39ene Carbnm Nanntllbes Carbnn Nannmbes wele Sm dlseuveed lu 1991 by he Japanese sumus Summ llllma Nanntubes are essemally any mp5 nfgaphme shee mlled mm uhes ald capped wuh half afullerme a eaeh end They eal he made by heanng gaphlte u almu 1200 C m m luell amumhee under u a m ed emdlums Because he carbnn atnms m hahuulh es are held tngelha39 hy nvalentbnnds he uhes are lmmmsely mngrabnut 100 umes that ufal eqmvalmt Strand hf s eel Thus there are umlemed uses as a supa39rstmng ma ellal valdmg he carbnn hexagnns are allgmed preusely wlth he lung ams umlehammhe he mammal ls al excellent eleemeal Enndudnr Thls behavmr duels he msslhlluy nfbundles nfnanntubes helllg he elemeal eqmvalmt nfnpncal bers Hnweva lthere ls a m he hexagnns gvmg a mual mmmmt he mazehal behaves as a Smcnndudnr 145 Chemxslxy of Carbon Two propemes of earbon enable n to form avast anay of compounds catenauon enan formanon andmulnple bondrng Carbon has the greatest tendency toward catenauon of all me elanents Condmons neeessary for earenanon Bondrng capanty z 2 Tendeney to bond wrun xtself Kmenc memess of eharns c has a rnuen greater propenst for catenauon than 5 c c and c 0 bonds are of eornparable strenth whde Sr 5 bonds are sxgn candy weaker than Sr 0 bonds Sr 5 bonds are rnuen rnore suseepnble to oendanon than are c c bonds and 7 Sr oe Sr oe enarns dominate the charmstzy of smeon bond energy bond energy bond bond kJ molquot kJ molquot C C 346 Si Si 222 C O 358 Si O 452 146 C also has a much greater propensity for multiple bond formation than Si The C30 bond energy is somewhat more than double that of Ci 0 but the longer SiO bond prevents effective p n p n overlap It has also been argued that the SiO bond has signi cant character due to p n d n backbonding 397 143 H3 143 c Si O Si O Si O H36 CH3 clH3 i143 n clH3 b d b 1 bond on energy bond on energy kJ mol 1 kJ mol l C O 358 Si O 452 CO 745 SiO Carbides Binary compounds of carbon with less electronegative elements other than H are called carbides These are typically hard highmelting solids which can be classi ed as either ionic covalent or metallic Ionic Carbides These are formed by the most electropositive elements Groups I and II and Al Most of these actually contain the dicarbide 27 ion C221 and react with water to form acetylene CaC2 s 2 H20 0 a CaOH2 aq C2H2 g BezC and A14C3 appear to contain C4 With such polarizing cations however there is likely considerable covalence although they do react with water to form methane BezC s 4 H20 0 a 2 BeOH2 s CH4 g 147 Covalent Carbldes Srhcon carblde 5rc and boron carblde Bc ac Examples of covalent carbldes Both are very had hlgTrmelung sohds slc ls prepaedby the reacuon of slo2 wth gaphlte at 2300 c tn a very energy lntenslve reacuon 8025 3cs i SiCs 20mg Metalllc carbtdes Metalllconntersnua1 carbldes ae those tn whrch carbon atoms t wthm holes tn the crystal latuce of ametal and ac usually formed by transluon metals The metal must adopt a close packed structure andbe large enoug1 gt 130 pm to accommodate the c atom wthm the octahedral holesln Its latuce Ifall the octahedral holes ae occupted the stolchromeay ls l 1 These matenals ae maemely had and hrgn melung They condrct elecmclty well and ac chemlcally reslstant Tungsten carblde wc ls used Exeenslvely tn cutung tools When the metal atoms are not large um enough to accommodate c atoms m the octahedral holesthe lance ls dstoned These compounds ac more reacuve than the true lntersuual carbldes FEZC cemenute ls such a carblde Mtcrocrystals of cemenute lmpm enhancedhadness to cabon steel tumumumm etueraroumumute n lumqu mm r um new more trauma nut a I39m Carbon Monom de Colorless odorless gas b p r 190 C Formedwhen cabon or carbon contarnlng compounds ac bumed wth a de ciency of q co bond ls exaemely short conslstent wth a CObond 148 Preparation of CO CO can be prepared in a number of ways Reduction of C02 C02 H2 C0 H20 Steam reforming of methane CH4 HZO CO 3H2 Decomposition of formic acid HOOZH sto4 HzO 1 C0g Reactions of CO CO undergoes a number of important reactions Reduction of metal oxides A 3Dg gt 2Fel Formation of methanol OO 2PL A 0amp0ng OX0 process coltggt 02H4ltggt mg A CszCHO Formation of transition metal carbonyls A N S 4 C0g gt Ni004 g 149 A more detailed discussion of transition metal carbonyls is available in sections 227229 In these compounds the metal has an oxidation state of O A wide variety of mono and polynuclear carbonyls are known with various binding modes for CO terminal bridging and capping O O C C l CO 0C l 39OO OC Md CO C quotI39 Fe CO OC Ni39 CO yr O l 00 O 4 n n o It 1 El pg tic CI I at quotChg LE i I sur fse If 39 h 25 39 lira1 Ile En m N am n co new a 43 r 3 r A 39 39 gt a 39 I I 391 an HA 3 I E Q 393 395 to E 393 Q g u n M quot Mm 39139 Fig HI iiIJ jI Th structures ulcdiliudmr metal curhmjyls 0 0 o o 8 C c 0 c o 8 0 o C 0 c0 C CO t cm W Eae 6 quot C 0 O l ltl c Ten OCRN 0 r r 0c 0 MC 6 c COCO OC ll 0 O C c 0 00 r 0 0 OC l Co M Ru Os 8 b g The structures of some trinuclear carbonyls a II b The structures of tetranuclear carbonyls Carbon Dioxide Carbon dioxide is a colorless odorless dense and relatively inert gas which does not burn and does not support combustion It will however react with buming metals 2Mgco2 azMgoC C02 is formed when carbon or carbon containing compounds are burned in excess 02 C02 does not exist as a liquid at normal atmospheric pressure A pressure of 6700 kPa is required to liquify C02 at 25 C Supercritical C02 is used to carry out a number of industrially important extractions Harlin Islamic I nTllll HUI K IJ39FESEEU WE If I P61 32 39l39cm pcrmilre 439 391 CS EC 3 Phase diagram 1410 Boudmg u cq Carbonroxygm bond length and energy are comment wth two c doublebonds slmpleLers theory hybndazanon theory and OCO molecular orbltal theory all suppon ths obsa39vauon um Makmbr elm mu mull ummk z x o mm m AcldrBase B ehavlor of cq co2 ls aLewls and ande anhydnde oftheweak dapron and carbonl and HZCOZ cozgngzoa H2C03aq K15 x 1039 HzCOzaq H20 HCO aq HO39aq K 743x107 Hco aqHZOl co aq ILO39aq K247x1039 However along uuo account the fact that only a the m majority of cq moleeules do not react the actual K10fH2COXls about 2 9 x10quot At pH 5 8 me neutnllzahon of cq occurs by hydration of cq co2 g HZO l HZCOK aq HZCOZ aq OH39 aq Hco aq HZO l 14 11 At pH gt10 the neutrahzataon of cq oeeurs by duect reaetaon ofco1 wrth OH co2 aq OH39 aq Hco aq Hco aq OH39 aq co aq 1120 1 co2 and the Greenhouse Effect The earths greenhouse effect or rad1anontxapp1ngquot 15 whatmakes Earth surtab1e forhfe as we know rt 5o1arradrataon 15 absorbedby the Earth39s surface and atmomhere and rermdAated m the form ofmfrared mdtanon The earths atmosphere eontatns traee gases HZO co cm 0 and N20 whreh absorb the m 39aredradaanon heat andrerradAatethe energy tn a11 duectmns Thesegases are referred to as gemhouse gases The Golddocks Pnnerp1e Venus 15 too hot Mars 15 too eolaL and Earth xsjusL ngnt Earth has an average surface temperature surtab1e for hfe as we know beeause ofthe nght kmd of atmosphere Venus39 atmosphere 96 cq 3 5 N2 nttrogen lt 1 co Ar so2 and H20 at apressure of9000 kPa and 45010 and Mars39 atmosphere 95 1 D C co2 at apressure of1 kPa andr50 c1 wou1o1be not be surtab1e or1rfe as we know rt H H H 1 z u n m nut 175mm 1 man Polyatomre molecules otherthan homonuelear dwtomms absorb mfraredradwnon andtherefore eontrrbute to the gemhouse etfeet mt W 43quot mt Wm 132mmquot water 5 me pYEdom nmt gemhouse gas39 but s H tlvmlwmul H 0 tum cor and HM atmosphene eoneentrataon and therefore rts effect on metequotgtth mentorn trsntntms the g1oba1 ebmate has remanedfaxrly eonstant Increases tn the atmomhene eoneentrataon of cq wr11resu1trn htgner average temperatures a tut phenomenon known as g1oba1 Warmmg 5 w Yen 1412 Carbonates and Hydrogen Carbonates Only the alkali metals other than Li form stable solid hydrogen carbonates which decompose on heating MH003 s A M2003 s Hzo I cog g The carbonate ion is quite basic due to its hydrolysis 0032 211 H200v HCOs 211 0H 211 Bonding in CO3239 CO bond lengths are identical but shorter than a C4 single bond The O bonding makes use of a set of sp2 hybridized orbitals on C leaving an unhybridized p orbital from C and a single p orbital on each 0 for nbonding M Carbon Disul de Carbon disul de is the sulfur analog of carbon dioxide with a linear geometry It is a colorless to pale yellow nonpolar volatile and toxic liquid bp 46 C It is prepared by passing methane over molten sulfur at 700 C and cooling the products to condense CSZ CH4g 4 81 i CSzg 2 H28 9 It is used as a solvent for nonpolar solutes like P4 as well as a starting material for other compounds 1413 Hydrogen Cyanide and Cyanides HCN is an extremely toxic gasliquid bp 26 C CN is a pseudohalide so HCN is a covalent molecular substance HCN is an extremely weak acid pKa 921 and cyanides are hydrolyzed to HCN in aqueous solution It is prepared either by the Degussa Process Pt 1200 C CH4g NH3 9 HCNg 3 H2 g or by the Andrussow Process PtRh 111 C 2CH4g2NH3g 302 2HCNg6H20 g Toxicity of CO and CN Even though CO and CN are isoelectronic their mechanisms of toxicity are di erent CO binds more strongly to hemoglobin than does 02 reducing the availability of hemoglobin for 02 transport Hbo2 CO HbCO 02 K 210 CN interferes with e transport by cytochrome oxidase c which is necessary for respiration and depends on the FenFe 1 redox couple CN coordinates to the Fe center in the cytochrome and stabilizes the FeIII interfering with electron transfer The most effective treatment for CO poisoning is oxygen therapy In accord with LeChatelier s Principle excess 02 will displace CO from hemoglobin Treatment for cyanide poisoning involves either conversion of CN to the less toxic SCN ion with thiosulfate rlDdamse CN39 203 SCN39 303239 or oxidizing Hb to metHb which binds CN more tightly than Hb or cytochrome c and can effectively remove it from the body HbFeH amp HbFeII 14 14 Srlreon Srlreon ls the seeondrnost abundant behmd only oxygen elernent m the earth39s erust at 27vn by rnass ltrs foundln yanous srheate rnrnerals eontarnrng 5H bonds Ultrapure slheon for sernreonduetor appheauons ls prepared by a mLLlnrstep proeess 510215 redueedto 5r uslng eoke A mum SOzs2Cs Sil 2co Iheresulung erude 5r ls ondzedrn astrearn ofHCl g to produee SrHClZ wheh ean be punfled to the ppb level by exhausuye dsullauon Sls3HClg EC chh H2g SrHClZ deeornposes spontaneously when heatedwrth H2 to 1000 C yleldmg extremely though not su iclen y pure 5r SiHClKQg H204 A Sis 3HClg lElElEI C Further punflcanon ls earned out by zone relinlng Whlch RWNE39V V 539 rehes on the faetthat rrnpunues wlll be excludedfrom the latuee when quurd 5r erystalhzes Uluapulc sl I Mohen SI Hmnng Coll V Duecnuu cull Inmcs Srlreon Dloxlde slllca l 5 Dewrte slrnrlar formulas cq and so2 are strueturally dsunet Whlle cq l3 ls a gas at room temperature due to weak dspersron forces 5ro2 ls hrgn melung1600 c eoyalentnetwork solldforreasonsprsvlously dlscussed Sllleals falrly unreaeuve however lt does reaet readily wnh HF and F2 t le2 s 6 HF aq e Sng39 aq 2H aq 2Hzo l As well as wrth strong bases 02 OH and fused earbonates 1415 5ro2 2Na0H NaZSlOK H20 For thrs reason solutrons ofHF anolNaOH as well as other strong bases are storeol rn plastre bottles Glasses and Srlreates Glasses are nonrtrysta lnemaeenals When erystallrne srlreon dloxldels heatedto above 2000 c anol allowedto eool rts vrseosrty graolrally rnereases untrl solldlfles wrthout erystallrzrng resultrng rn what we know as quartz glass Whlle quartz glass has a number ofrmportant eharaetenstres low coe iclmt of enpansronresulungrn eneellertthermal shoek resrstanee anol tranmareney rn the UV the hrgn worlnng temperature of quartz makes rt to expenslve for routzne applreatrons The vrseosrty of the quurol and rts worlnng temperature ear be reolueeol by breaklng some othe Sr or 5r bndgng bonds foundln 5ro2 Addmon of Nap usually as NaZCOK to molten srlrea reoluees the vrseosrty and Lhar ore the worlnng temperature by brealnng some ofthe bndglng bonols Soda glass has a low worlnng temperature but poor thermal shoekresrstaree and rt tends to dlssolve rn water Addmg Cao reoluees the solubrlrty Most of theglassuseoltoday wrndowsbottles ete rs sodae lrme srlrea glass The addmon oquOZ to soolaglassreoluees the solubrlrty as well as the thermal expanle eoelfrerert Borosrlreate Pyrex m glasses are useol when thermal shock resrstanee rs neeoleol M rrrrtp nrm aorturm quoturtrwr 14 16 Silicates Depmdmg m be nurnber ofbndgng bonds m so2 that are broken vanous srbeaze amons are possble Kali me bndgng bonds are brokmthereshdtxsdqetetxahedral onhosxhcate ron soquot so2 2 NaZCOX Na SxO 2 co2 When halme bndgng bonds are broken so2 0139 a so andLheresultxs almearcham sxhcate structure 0 0 u 1 u u Su u 1 Si u o o r0 o o x 0 s m 5n n s w r w w o 0 1 o 0 Moon urn m Chum srofrzymkemy A double cham or m mee band oeeurs m a class of mmemls called arnpnrboles Asbestos and relaeedmmerals have nus stxucmre whmh resuus m uner brous nature a of me bndgrng bonds are broken 4 so2 3 0139 soon 0 0 w 1 S 0 s o u u 0 0 5r 1 S r w o 0 0 x u 51 5r men n n o 0 s39 0 5 0 y 0 w u o w r nonean r unu in Band snouhnmpmuoxesx 14 17 Lu uue sheets resultmlayeredmmerals sueh as mxca talc andvanous clays Thxs structure results from me breakmg of VA othe bndgng bonds 2502 0139 a 5205 in sheescSi2 5 39zmiuasca1cclaysem 1418 Silanes Monosilane is prepared by heating SiO 2 with LiA1H4 at 150 to 170 C Higher silanes are prepared by photolyzing mixtures of SiH4 and H2 in a reaction where SiH2 might be an intermediate Of the silanes only monosilane SiH4 and disilane SizH6 are inde nitely stable at 25 C Higher silanes are spontaneously ammable in air Si4H10 132 02 4 SiO2 5 H20 Silanes are stable to water and dilute mineral acids but subject to rapid base hydrolysis SizH6 4 n H20 4 2 Si02 n H20 7 H2 Germanium Germanium and silicon both have a diamond structure The graphite structure is unique to carbon Like Si germanium is used in semiconductor deVices Germanium is prepared by the reduction of its oxide with either carbon or hydrogen GeO2 2C 4 Ge 2C0 Ge02 2H2 HGe 2H20 1419 Tin and Lead Tin has two common allotropes Gray at tin dull gray in color brittle diamond structure semiconductor p 575 g 39 cm 3 at 20 C stable below 13 C White 13 tin silva in color with charact istic metallic lusta malleable tetragonal lattice mdallic conductor p 731 g 39 cm 3 at 20 C stable above 13 C 13 C 232039 octln gt tln gt llquld Lead exists only in the ccp mdallic form re ecting vay low stability of the Pbin bond It is a very dense very soft dark gray metal Lead occurs almost exclusively as the mineral galena PbS It is extracted by oxidizing the PbS to PbO and SOZ and reducing the PbO with coke PoSs302gA 2PoOZSOZg 1105 Cs A Pea CDQg Environmental concems include production of SOZ which contributes to acid rain and release of toxic lead dust 1420 Oxides of Tin and Lead Tin IV oxide SnOz is the more stable oxide of tin while of lead II oxide PbO is the more stable oxide of lead PbO occurs in two forms litharge red in color with a layered structure and massicott yellow in color with a chain structure Pb02 is chocolate brown in color It is chemically stable and a good oxidizing agent In addition red lead Pb304 lead II lead IV oxide can be prepared by heating either PbO or Pb02 in air It behaves chemically as if it were a mixture of PbO and PbOz but the structure involves PbIVO6 octahedra linked in chains by the sharing of opposite edges The chains are linked by Pb1 ions each bound to three 0 atoms Chlorides of Tin and Lead Tin IV chloride is atypical covalent metal chloride It is an oily liquid which reacts with ambient moisture to give a hydrated oxide of tin which is represented as SnOH4 SnC4 4 H20 0 3110H4 s4HCl g Lead IV chloride is also an oily liquid yellow in color which decomposes when exposed to ambient moisture explosively when heated PbBr4 and PbI4 do not exist because Br and I are not suf ciently reducing to stabilize PbIV Lead II chloride is an insoluble white solid with an ionic crystal lattice but tinII chloride exhibits covalent character as evidenced by bridging chlorides and solubility in low polarity solvents In the gas phase SnCl2 is bent with a bond angle of about 95 suggesting that the orbitals used for bonding are essentially pure p orbitals SnClZ does not exhibit Lewis base behavior but instead acts as a Lewis acid 11012 or SnClg39 The lone pair appears to occupy a spherical s orbital
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