main group chemistry notes

7/29/2019 main group chemistry notes

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The Group 18 (Noble Gas) elements:The Group 18 (Noble Gas) elements:Helium, Neon, Argon, Krypton, Xenon and RadonHelium, Neon, Argon, Krypton, Xenon and Radon

TheThe noblenoble gassesgasses havehave alsoalso beenbeen calledcalled thethe rareraregases,gases, andand thethe inertinert gasesgases. . NoneNone of of thethe namesnames is is

particularlyparticularly suitablesuitable; ; withwith extensiveextensive chemistry,chemistry,xenonxenon isis notnot inert,inert, andand argonargon isis almostalmost 3030 timestimesmoremore abundantabundant thanthan carboncarbon dioxidedioxide inin air air

Something to know about:Something to know about: TheThe greater greater reactivityreactivity of of xenonxenon compoundscompounds comparedcompared to to thethe

other other elementselements. .

TheThe stabilitystability of of xenonxenon compoundscompounds containingcontaining electronegativeelectronegativeelementselements (O(O andand F)F)

TheThe reactivityreactivity of of noblenoble gasgas fluoridesfluorides asas fluoridefluoride ionion donorsdonors andandacceptorsacceptors


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Extremely high ionization energyExtremely high ionization energy

Assumption: Not suitable for making chemical compoundsAssumption: Not suitable for making chemical compounds

FirstFirst xenonxenon compoundscompounds werewere synthesizedsynthesized in in 19621962, , sincesince thenthen thethe

chemistrychemistry of of xenonxenon isis extensiveextensive. .

A few compounds of krypton have also been reported.A few compounds of krypton have also been reported.

TheThe chemistrychemistry of of manymany noblenoble gasgas compoundscompounds are are analogousanalogous to tothosethose of of heavier heavier GroupGroup 1717 elementselements. .

VSEPRVSEPR isis aa powerfulpowerful techniquetechnique for for rationalizingrationalizing andand predictingpredicting thetheshapesshapes of of manymany noblenoble gasgas compounds,compounds, whichwhich havehave relativelyrelatively largelarge

number number of of electronelectron pairspairs inin thethe valencevalence shellshell of of thethe centralcentral atomatom. .


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NobleNoble gasesgases havehave filledfilled shells,shells, andand soso inin order order toto formform chemicalchemicalcompounds,compounds, electronselectrons mustmust bebe promotedpromoted intointo thethe nextnext shellshell. .

DependingDepending onon thethe number number of of electronselectrons promoted,promoted, compoundscompounds of of thethe noblenoble gasesgases inin oxidationoxidation statesstates + +22,, ++44,, ++66 andand ++88 havehave allallbeenbeen synthesizedsynthesized. .

,,removedremoved andand therethere isis decreasedecrease in in firstfirst ionizationionization energyenergy. .

AsAs aa resultresult therethere areare manymany xenonxenon compoundscompounds but but aa fewfew for for krypton,krypton, andand nonenone havehave beenbeen isolatedisolated for for argonargon. .


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AllAll compoundscompounds tendtend toto bebe strongstrong oxidizingoxidizing agents,agents, andand thethefluoridesfluorides areare alsoalso powerfulpowerful fluorinatingfluorinating agentsagents. .

TheThe formationformation of of anionicanionic noblenoble gasgas compoundscompounds (such(such asas CesiumCesiumneonideneonide, , CsCs ++NeNe --)) withwith electropositiveelectropositive metalsmetals isis anan intriguingintriguingpossibility,possibility, thoughthough nonenone hashas yetyet beenbeen isolatedisolated. .

G. H. Purser, J. Chem. Educ., 1988, 65, 119G. H. Purser, J. Chem. Educ., 1988, 65, 119

chemistry,chemistry,

See the ref See the ref .: P. Laszlo and G. I..: P. Laszlo and G. I. SchrobilgenSchrobilgen, , AngewAngew. Chem. Int. Ed. Engl. 1988, 27, 479.. Chem. Int. Ed. Engl. 1988, 27, 479.


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OccurrenceOccurrence

AllAll of of thethe elementselements existexist asas highlyhighly unreactiveunreactive monoatomicmonoatomic gases,gases, withwithveryvery lowlow boilingboiling pointspoints. .

ArgonArgon isis thethe mostmost abundant,abundant, comprisingcomprising of of 00..9393%% of of thethe atmosphereatmosphere. .Helium,Helium, neon,neon, kryptonkrypton andand xenonxenon areare tracetrace constituentsconstituents of of air air..

AllAll isotopesisotopes of of radonradon areare radioactive,radioactive, andand areare formedformed naturallynaturally fromfrom thethedecaydecay of of heavyheavy radioisotopesradioisotopes suchsuch asas thosethose of of radiumradium andand uraniumuranium. .

NobleNoble GasGas ClathratesClathratesInIn thethe 19201920ss andand 19301930ss therethere waswas considerableconsiderable interestinterest in in materialsmaterialsformedformed betweenbetween noblenoble gasesgases (particularly(particularly Ar Ar,, Kr Kr andand XeXe)) andand stronglystrongly H H--bondingbonding compoundscompounds suchsuch asas water water andand polyphenolspolyphenols. .

Later Later itit waswas shownshown thatthat theythey areare notnot chemicalchemical compoundscompounds but but clathrateclathratecompoundscompounds (also(also knownknown asas inclusioninclusion compounds),compounds), wherewhere thethe gasgasatomsatoms occupyoccupy voidsvoids inin thethe HH--bondedbonded latticelattice of of thethe hosthost compoundcompoundwhenwhen thethe hosthost isis crystallizedcrystallized under under a a noblenoble gasgas atmosphereatmosphere. .


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XenonXenon formsforms a a clathrateclathrate withwith water water of of approximateapproximatecompositioncomposition Xe Xe(H(H

22O)O)

nn(n(n == 55 or or 66),), whichwhich hashas aa meltingmelting

pointpoint of of 2424 ooCC..

Noble gas halidesNoble gas halides MostMost importantimportant compoundscompounds of of noblenoble gasesgases

FluorineFluorine is is thethe mostmost electronegativeelectronegative elementelement andand isisableable totostabilizestabilize thethe highlyhighly oxidizingoxidizing noblenoble gasgas compoundscompounds. .

noblenoble gasgas atomatom inin aa voidvoid inin thethelatticelattice. . HydrogenHydrogen atomsatoms of of water water moleculesmolecules areare omittedomitted for for clarityclarity

TheThe vastvast majoritymajority of of compoundscompounds are are fluoridesfluorides of of xenon xenon (a(a fewfew of of Kr)Kr) thoughthough somesome chemistrychemistry of of radonradonisis known,known, hamperedhampered by by itsits radioactivityradioactivity and andavailabilityavailability in in onlyonly smallsmall quantitiesquantities. .

FluoridesFluorides areare thethe mostmost importantimportant compoundscompounds formedformed byby thethe noblenoble gasesgases


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KryptonKrypton difluoridedifluoride

Only known halide is KrFOnly known halide is KrF 22 synthesized by passing an electricalsynthesized by passing an electricaldischarge through a fluorinedischarge through a fluorine- -krypton mixture.krypton mixture.

KrFKrF 22 is a powerful fluorinating agent and is more reactive than XeFis a powerful fluorinating agent and is more reactive than XeF 22..It will oxidizeIt will oxidize XeXe to XeFto XeF 66 and metallic gold to AuFand metallic gold to AuF 66--..

++ ++

7KrF7KrF 22 + 2Au+ 2Au 2[2[KrFKrF]]++[AuF[AuF 66]]-- + 5Kr + 5Kr


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Xenon FluoridesXenon Fluorides

AA xenonxenon fluoride,fluoride, XePtFXePtF 66,, waswas thethe firstfirst noblenoble gasgas compoundcompound to to bebesynthesizedsynthesized by by reactionreaction of of XeXe withwith strongstrong oxidantoxidant PtFPtF 66,, andand later later shownshowntoto bebe probablyprobably a a mixturemixture of of [[XeFXeF]]++[PtF[PtF 66]]-- andand [[XeFXeF]]++[Pt[Pt 22FF 1111 ]]-- ..

XenonXenon formsforms threethree neutralneutral fluorides,fluorides, XeFXeF 22,, XeFXeF 44 andand XeFXeF 66,, byby thethereactionreaction of of fluorinefluorine andand xenonxenon under under differentdifferent conditionsconditions. .

Simplest method involves exposing a fluorineSimplest method involves exposing a fluorine- -xenon mixture (containedxenon mixture (containedin a dry glass bulb) to sunlight; colorless crystals of XeFin a dry glass bulb) to sunlight; colorless crystals of XeF 22 are depositedare deposited

..

KrFKrF 22 is a powerful fluorinating agent and is more reactive than XeFis a powerful fluorinating agent and is more reactive than XeF 22..

It will oxidizeIt will oxidize XeXe to XeFto XeF 66 and metallic gold to AuFand metallic gold to AuF 66--..

3KrF3KrF 22 ++ XeXe XeFXeF 66 + 3Kr + 3Kr

7KrF7KrF 22 + 2Au+ 2Au 2KrF2KrF++

AuFAuF 66--

+ 5Kr + 5Kr


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TheThe sunlightsunlight causescauses dissociationdissociation of of thethe relativelyrelatively weaker weaker F F--FF bondbond inin FF22

totoformform FF atoms,atoms, whichwhich thenthen reactreact withwith XeXe..

WithWith larger larger ratiosratios of of FF toto XeXe,, higher higher temperaturestemperatures and and higher higher pressures,pressures,XeFXeF 44 andand XeFXeF 66 cancan bebe synthesizedsynthesized. .

ShapesShapes: :

F F

XeFXeF 66 isis fluxionalfluxional inin thethe gasgas phase,phase,interchanginginterchanging betweenbetween structuresstructureswherewhere thethe lonelone pair pair pointspoints throughthroughthethe centrecentre of of anan FF33 triangletriangle (one(one

Xe

F

XeF

F

F

F

F

F

F

F

FXe

face)face) of of aa distorteddistorted octahedraloctahedral XeFXeF 66moleculemolecule. . TheThe lonelone pair pair isis inin aasphericallyspherically inactiveinactive s s--orbitalorbital. .

XeF 2 XeF 4 XeF 6


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All of the xenon fluorides are powerful fluorinating agents, able to oxidizeAll of the xenon fluorides are powerful fluorinating agents, able to oxidize

a wide range of compounds.a wide range of compounds.

InIn manymany casescases XeFXeF 22 isis aa veryvery selectiveselective oxidant,oxidant, ableable toto oxidizeoxidize thethe centralcentralheteroatomheteroatom of of aa mainmain groupgroup compoundcompound (such(such asas As,As, P,P, etcetc. .)) butbut notnotorganicorganic substituentssubstituents (methyl(methyl or or phenyl)phenyl) bondedbonded toto itit..

MeMe 33As + XeFAs + XeF 22 MeMe 33AsFAsF 22 + Xe+ Xe

++ ++

XeFXeF 22 also oxidizes water to oxygen, while XeFalso oxidizes water to oxygen, while XeF 44 can oxidize platinum metalcan oxidize platinum metalto PtFto PtF 44

2H2H 22O + 2XeFO + 2XeF 22 OO 22 + 4HF + 2Xe+ 4HF + 2Xe

XeFXeF 44 + Pt+ Pt PtFPtF 44 + Xe+ Xe


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Reactions of noble gas fluorides with fluoride ionReactions of noble gas fluorides with fluoride ion

acceptors and donorsacceptors and donorsChemistry is extensiveChemistry is extensive

NobleNoble gasgas fluoridesfluorides reactreact withwith strongstrong fluoridefluoride ionionacceptors,acceptors, EFEF 55 of of AsFAsF 55,, SbFSbF 55,, BiFBiF 55,, Ta,Ta, RuRu or or PtPt..

XeFXeF 22 formsforms thethe greatestgreatest number number of of compoundscompounds by by thisthis

typetype of of reactionreaction followedfollowed byby XeFXeF 66 andand XeFXeF 44..

KrFKrF 22 formsforms manymany similar similar compoundscompounds. .

WhileWhile transferringtransferring thethe fluorides,fluorides, cancan bebe fullyfully transferredtransferred to to thetheLewisLewis acidacid MFMF55 leavingleaving cationiccationic xenonxenon species,species, butbut inin mostmost casescasesfluoridefluoride isis onlyonly partiallypartially transferred,transferred, resultingresulting in in compoundscompounds withwithXeXe FF EE fluoridefluoride bridgesbridges. .


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Different types of Different types of cationscations and anions are formed depending on theand anions are formed depending on the

stoichiometrystoichiometry of noble gas fluoride to EFof noble gas fluoride to EF 55..

XeFXeF 2(s)2(s) + AsF+ AsF 5(l)5(l) [[XeFXeF]]++[AsF[AsF 66]]--(s)(s) (1:1 ratio)(1:1 ratio)

When a 2:1 ratio is used, the adducts tend to containWhen a 2:1 ratio is used, the adducts tend to contain cations cations withwithXeXeFFE bridges.E bridges.

FAs

F FF

Xe

F Xe F214 pm

150 o

F

Sb

F

FF

FF

FXe F F FF

FF

F

[Xe[Xe 22FF33]]++ cationcation [Sb[Sb 22FF1111 ]] anionanion[[XeFXeF]]++[AsF[AsF 66]]

Noble gas fluorides can act as fluoride acceptors or donors to give anions or Noble gas fluorides can act as fluoride acceptors or donors to give anions or

cationscationsXeFXeF 44 + F+ F -- [[XeFXeF 55]]--

(also, [(also, [XeFXeF 77]]--, [, [XeFXeF 88]]22-- fromfrom XeFXeF 66,, XeFXeF 77 by adding one or two Fby adding one or two F -- ions)ions)


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XenonXenon- -oxygen compoundsoxygen compounds

Results from hydrolysis of the fluorides XeFResults from hydrolysis of the fluorides XeF 44 and XeFand XeF 66..Hydrolysis of XeFHydrolysis of XeF 22 results in oxidation of water to oxygen.results in oxidation of water to oxygen.

6XeF6XeF 44 + 12H+ 12H 22OO 4Xe + 2XeO4Xe + 2XeO 33 + 24HF + 3O+ 24HF + 3O 22

XeFXeF 66 + 3H+ 3H 22OO XeOXeO 33 + 6HF+ 6HF

XeOXeO 33 is a highly explosive white solid, soluble in water (not ionized)is a highly explosive white solid, soluble in water (not ionized)

InIn strongstrong alkalinealkaline solution,solution, however,however, XeOXeO33

behavesbehaves as as aa weakweak acid,acid, givinggivingxenatexenate(VI)(VI) anion,anion, [XeO[XeO 33(OH)](OH)] --,, byby additionaddition of of OHOH --

XeOXeO 33 + OH+ OH -- [XeO[XeO 33(OH)](OH)] --

XenateXenate(VI)(VI) anionanion isis unstableunstable in in aqueousaqueous solution,solution, andand undergoesundergoes a adisproportionationdisproportionation reactionreaction to to givegive xenonxenon gasgas andand thethe xenatexenate(VIII)(VIII) anion,anion,XeOXeO 6644--,, whichwhich containscontains xenonxenon inin ++88 oxidationoxidation statestate. .

2XeO2XeO 33(OH)(OH) -- + 2OH+ 2OH -- XeOXeO 6644-- ++ XeXe + O+ O 22 + 2H+ 2H 22OO


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XeFXeF 66 + H+ H 22OO XeOFXeOF 44 + 2HF+ 2HF

XeFXeF 66 + NaNO+ NaNO 33 XeOFXeOF 44 ++ NaFNaF + FNO+ FNO 22

XeFXeF 66 ++ POFf POFf XeOFXeOF 44 + PF+ PF 55

The reaction of XeFThe reaction of XeF 66 with Nawith Na 44XeOXeO 66 gives thegives the oxyfluoridesoxyfluorides XeOFXeOF 44 and XeOand XeO 33FF22;;XeOXeO 22FF 22 is also known.is also known.

Other xenonOther xenon- -oxygen compounds can be formed from XeFoxygen compounds can be formed from XeF 22, XeF, XeF 44 and XeFand XeF 66 bybysubstitution of one or more fluorides b reaction of stronsubstitution of one or more fluorides b reaction of stron ox acids ox acids XOH suchXOH such

as CFas CF 33SOSO 33H, MeSOH, MeSO 33H, CFH, CF 33COOH, FSOCOOH, FSO 33H or TeFH or TeF 55OH, with elimination of HFOH, with elimination of HF

FFXeXeF + XOHF + XOH FFXeXeOX (+HF)OX (+HF) XOXOXeXeOX (+HF)OX (+HF)

Alternatively, fluoride exchange yields analogous productsAlternatively, fluoride exchange yields analogous products

XeFXeF 66 + 2B(OTeF+ 2B(OTeF 55))33 XeXe(OTeF(OTeF 55))66 + 2BF+ 2BF 33

The compounds have similar shapes to fluorides, e.g. XOThe compounds have similar shapes to fluorides, e.g. XO- -XeXe--OX and XeFOX and XeF 22 areare

both linear.both linear.


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Xenon and Krypton compounds with bonds to elements other than O and FXenon and Krypton compounds with bonds to elements other than O and F

XeFXeF 22 +B(C+B(C 66FF55))33 [C[C 66FF55Xe]Xe] ++[C[C 66FF55BFBF 33]]-- +[C+[C 66FF55Xe][(CXe][(C 66FF55))22BFBF 22]]--

AlkynylAlkynyl species of the type [Rspecies of the type [R CCCCXeXe]]++, where R can be a range of non, where R can be a range of non- -fluorinated groups such as ethyl or fluorinated groups such as ethyl or SiMeSiMe 33 have been made.have been made.

Extensive organic chemistry is awaited or awaits discovery.Extensive organic chemistry is awaited or awaits discovery.

[C[C 66FF55Xe]Xe] ++ ++ ClCl -- CC66FF55XeClXeCl FFF

F F

Xe+

TheThe [C[C 66FF55Xe]Xe] ++ cationcation inin MeCNMeCNsolutionsolution getget solvatedsolvated to to givegive[C[C 66FF 55Xe(Xe(NCMeNCMe)])]++ ;; whichwhich hashas aalinear linear geometrygeometry

main group chemistry notes

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