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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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Markscheme

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