Giant Covalent Bonding

Giant Covalent BondingAllotropic forms of carbonFun factsan element is said to exhibit allotropy ifit occurs in 2 or more formsDiamondevery carbon atom is bonded to4 other carbon atoms by strong covalent bondsgiant covalent structuremade up of only carbon atomsHigh melting pointlarge amount of energy required tobreak the strong covalent bonds between carbon atomsin the giant molecular structurenon - conductor of electricityno delocalised electrons as all valenceelectrons of each carbon atoms are usedfor covalent tbondingGraphitefound in sandconsists of seperate layers of carbon atomscarbon atoms are arranged in regular hexagonsin flat parallel layerscarbon forms strong covalent bonds with3 other carbon atoms forms rings of 6 carbon atoms which are joined together to form 2 - dimensional layersno strong bonding in between layersthey are easily seperable from each otherheld together by weak forces of attractionso the layers slide overeach other easily whena force is appliedaccounts for softness andlubricating power of graphitephysical propertieshigh melting and boiling pointsforces of attraction between layers are weakbut a lot of energy is still needed tobreak the strong covalent bonds between carbon atoms within layersthis can cause a change of stateGood conductor of electricitySoft and slipperyeach carbon atom has 1 valence electronthat isn't used to form covalent bondsdelocalised electrons move freelyalong layers from one C.A. to anotherwhen graphite is connected to a circuitthis causes an electric current to flow,causing graphite to conduct electricitywhen a force is appliedweak forces of attraction betweenthe layers of carbon atoms are easily overcomeso layers can easily slide over one anotherSilicon dioxidegiant covalent structureeach silicon atom is bondedto 4 oxygen atomseach oxygen atom is bonded to 2 oxygen atomsatoms are held together by strong covalent bondshigh melting pointsstructure similar to diamondsimilar physical propertiesused to produce glassFullerenea molecule made up of carbon atomsarranged in the form of a hollow spherecylindercalled 'buckyballs'called 'carbon nanotubes'amorphous forms of carbonmost reactive form of carbondoes not have any crystalline structureburns relatively easily in airserving as a fuelhas structural features of graphitehas sheets and layersatomic structure is irregularComparing the different structures in mattercovelent substancesgiant structuressummary of 4 structures in matter:simple molecular structuregiant covalent structurehydrogen, nitrogen, carbon dioxideexists as simple moleculeslow melting and boiling pointssoluble in organic solvents but not in waterdoesn't conduct electricityin any statediamond, graphite, silicond dioxideexists as a giant networkof covalently bonded atomshigh melting and boiling pointsdoes not conduct electricity(except graphite)giant ionicgiant metallicgiant covalentbondingelectrostatic attraction betweenoppositely charged ionsmelting and boiling pointshighsoulbility in waterusually solublesolubility in organic solventsinsolubleelectrical conductivitynon - conductor in solid state,but conductor in molten and aqueous statesbondingelectrostatic attraction between metalcations and 'sea of mobile electrons'melting and boiling pointshighsolubility in waterinsolublesolubility in organic solventsinsolubleelectrical conductivityconductor in solid and molten statesbondingelectrostatic attraction betweenshared electrons and positivenuclei of the atomsmelting and boiling pointshighsolubility in waterinsolublesolubility in organic solventsinsolubleionicsimple moleculargiant covalentexamplesodium chlorideparticles presentcations, anionsbondingionic bondelectrostatic attraction betweenoppositely charged ionsmelting and boiling pointshighphysical state at r.t.p.solidsolubilityin watersolublein organic solventsinsolubleelectrical conductivitygood conductor in moltenand aqueous statesnon conductor in solid statesdue to mobile ionsdue to ions infixed positionsmetallicexampleiron, nickel, steelparticles presentmetal cations, sea ofdelocalised electronsbondingmetallic bondingelectrostatic attraction betweenmetal cations and sea of delocalisedelectronsmelting and boiling pointshighphysical state at r.t.psolidsolubilityin waterinsolublein organic solventsinsolubleelectrical conductivitygood conductor inmolten and solid statesexamplecarbon dioxideparticles presentsimple moleculesconsisting of neutral atomsbondingcovalent bonds withinatoms of moleculesmelting and boiling pointslowphysical state at r.t.pliquid or gassolubilityin waterin organic solventsinsolublesolubleelectrical conductivitynon - conductordue to absence ofmobile charge carriersexamplegraphitediamond, silicon dioxideparticles presentatomsparticles presentatomsbonds between particlescovalent bonds throughout thegiant strcuturebonds between particlescovalent bonds between atomswithin the layermelting and boiling pointshighmelting and boiling pointshighsolubilityinsoluble in any solventsolubilityinsoluble in any solventconduction of electricityconduction of electricitygood conductordue to mobile and declocalised electronsalong the layersnon - conductordue to absence of delocalised electrons
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