Bonding Structure Shapes
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Transcript of Bonding Structure Shapes
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Bonding,structureandtrends
(periodicity)
Bondingandstructurerevision
Objec
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Defini
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Pastpaperques
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Markscheme
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Dotandcrossdiagrams-COVALENT
Remember
ShowsharingOverlaportouchcircles Showouterelectronseasytoforgetforhalogens
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Markscheme
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Markscheme
Da
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Markscheme
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Metallicbonding
Defini
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Markscheme
Shapesofmolecules
Electronpairsrepelensuringbondsareasfarawayfromeachotheraspossible.
Lonepairsrepelmorethenbondingpairs
Todetermineshape/bondangledecidehowmanybondingpairsandhowmanylonepairs
thereare
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Shapesofmolecules-allbondingpairs
Shapesofmoleculeswithlonepairs
Commonexamples
Waterbent2LP SO2bent1LP
Ammoniapyramidal1LP
XeF4squareplanar2LP
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Markscheme
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Markscheme
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Markscheme
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Structures
Ionic=giantioniclace
Metallic=giantmetalliclace
Covalent
1. Simplemolecular2. Simplemolecularlace3. Giantcovalentstructure
Giantioniclace
HighMPandBPduetostrongionicbonding SolubleinwaterasionscanbecomesolvatedConductswhenmoltenordissolvedasionscanmove
ExamplesNaCl,MgCl2.
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Giantmetalliclace
HighMPandBPduetostrongmetallicbonding-increasesalongaperiod(egNa,Mg,
Al)duetoincreasingca
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Markscheme
Simplemolecular
LowMPandBPasneedtobreakweakintermolecularforcessuchasinstantaneous
dipole-induceddipole,permanentdipole-
permanentdipoleandhydrogenbonding
Examples:H2O,CO2,N2,F2,SF6Nomobilechargecarriers(electronsorions)sodonotconduct
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GiantCovalentLace
HighMPandBPduetostrongcovalentbonds Generallydonotconduct(exceptgraphite*) Insoluble
Examples:
Si,C(diamond,graphite)
*Graphiteconductselectricitybecauseofdelocalisedelectronsbetweenitslayerstructure.Thereareweakintermolecularforcesbetweentheselayerswhichiswhygraphiteissoanddiamondishard.
[5]
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Markscheme
Simplemolecularlace
LowMPandBPasneedtobreakweakintermolecularforcessuchasinstantaneous
dipole-induceddipole,permanentdipole-
permanentdipoleandhydrogenbonding
Examples:I2,H2O(ice),P4Donotconduct
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Intermolecularforcesinsimplecovalentstructures
Thesearetheforcesholdingmoleculestogether
insimplecovalentstructures/molecules/
monatomicgases.
PermanentdipolepermanentdipoleVanderWaalsHydrogenBonding
Dipoledipoleinterac
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VanderWaalsForces
All atoms and molecules contain fast moving electrons.
At some point in time more electrons may be on one side of the
molecule than the other causing instantaneous dipoles in themolecule
ImagineamoleculewhichhasaINSTANTANEOUSpolaritybeing
approachedbyonewhichhappenstobeen
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Markscheme
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As you go down the group is that the number ofelectrons increases, and so also does the radius of
the atom. "This makes the atom more polarisable and so the
Van der Waals forces increase."This increases the boiling point."
helium -269C
neon -246C
argon -186C
krypton -152C
xenon -108C
radon -62C
Noblegases
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Markscheme
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Molecularmassandshape
HeaviermoleculescontainmoreelectronsandgenerallyhavestrongerVanderWaalsforces.
Straightmoleculescanapproachmorecloselythanbranchedmolecules.ThismeanstheVan
derWaalsforcesarestronger.
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Pastpaperques
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Theoriginofhydrogenbonding
Tohaveahydrogenbondyouneed:
1. Hydrogen;bondedto2. Nitrogen,oxygenorfluorine(themostelectronega
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Theanomalousproper
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Markscheme
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Proper
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Markscheme
Pastpaperques
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Markscheme
Proper
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Pastpaperques
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Proper
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[6]
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Electronega
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Predictthepolarity-AfL
Drawthedipole(s)forthefollowingmolecules. Egwater
Ammonia
Hydrogenchloride Carbontetrafluoride Di-chloro,di-fluoromethane
Isthemoleculepolar?
Formoleculesthataresymmetrical,thedipolesofanybondswithinthemoleculemaycancelout.
ForexampleCCl4orCBr2CBr2.Wecansaythatthecentreofposi
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Pastpaperques
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Pastpaperques
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Whodiscoveredtheperiodictable?
Mendeleevwasthefirsttopublish(in1869)
aversionoftheTablethatwewould
recognisetoday
butdoeshedeserveallthecredit?
Otherkeyfiguresinclude:
JohnNewlands(1March1865),LotharMayer(1868)
Alexandre-EmileBguyerdeChancourtois(1862)
Inthemodernperiodictableelementsarearrangedinorderoftheiratomicnumber.
Eachhorizontalrowiscalledaperiod. Eachver
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Periods(horizontal)
Elementsshowgradualchangesinproper
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Markscheme
Pastpaperques
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Markscheme