AQA GCSE Chemistry PDF - Atomic Structure & Periodic Table

AQA​ ​GCSE​ ​Chemistry Topic​ ​1:​ ​Atomic​ ​Structure​ ​and​ ​the Periodic​ ​Table A​ ​simple​ ​model​ ​of​ ​the​ ​atom,​ ​symbols,​ ​relative​ ​atomic​ ​mass, electronic​ ​charge​ ​and​ ​isotopes Notes...

AQA​ ​GCSE​ ​Chemistry Topic​ ​1:​ ​Atomic​ ​Structure​ ​and​ ​the Periodic​ ​Table A​ ​simple​ ​model​ ​of​ ​the​ ​atom,​ ​symbols,​ ​relative​ ​atomic​ ​mass, electronic​ ​charge​ ​and​ ​isotopes Notes (Content​ ​in​ ​bold​ ​is​ ​for​ ​Higher​ ​Tier​ ​only) www.pmt.education Atoms,​ ​elements​ ​and​ ​compounds Atoms​ ​make​ ​up​ ​all​ ​substances​ ​and​ ​are​ ​the​ ​smallest​ ​part​ ​of​ ​an​ ​element​ ​that​ ​can​ ​exist Chemical​ ​symbols​ ​represent​ ​an​ ​atom​ ​of​ ​an​ ​element​ ​e.g.​ ​Na​ ​represents​ ​an​ ​atom​ ​of sodium Compounds​ ​are​ ​formed​ ​from​ ​elements​ ​by​ ​chemical​ ​reactions.​ ​Chemical​ ​reactions always​ ​involve​ ​the​ ​formation​ ​of​ ​one​ ​or​ ​more​ ​new​ ​substances,​ ​and​ ​often​ ​involve​ ​an energy​ ​change Compounds​ ​contain​ ​two​ ​or​ ​more​ ​elements​ ​chemically​ ​combined​ ​in​ ​fixed​ ​proportions and​ ​can​ ​be​ ​represented​ ​by​ ​formulae​ ​using​ ​the​ ​symbols​ ​of​ ​the​ ​atoms​ ​from​ ​which​ ​they were​ ​formed​ ​e.g.​ ​HCl​ ​is​ ​a​ ​compound​ ​containing​ ​1​ ​atom​ ​of​ ​hydrogen​ ​and​ ​1​ ​of​ ​chlorine per​ ​molecule ​ ​Compounds​ ​can​ ​only​ ​be​ ​separated​ ​into​ ​elements​ ​by​ ​chemical​ ​reactions Mixtures A​ ​mixture​ ​consists​ ​of​ ​two​ ​or​ ​more​ ​elements​ ​or​ ​compounds​ ​not​ ​chemically​ ​combined together.​ ​The​ ​chemical​ ​properties​ ​of​ ​each​ ​substance​ ​in​ ​the​ ​mixture​ ​are​ ​unchanged.​ ​(this is​ ​different​ ​to​ ​a​ ​compound) Can​ ​be​ ​separated​ ​by:​ ​filtration,​ ​crystallisation,​ ​simple​ ​distillation,​ ​fractional​ ​distillation and​ ​chromatography.​ ​These​ ​are​ ​physical​ ​processes,​ ​so​ ​do​ ​not​ ​involve​ ​chemical​ ​reactions and​ ​no​ ​new​ ​substances​ ​are​ ​made. ​ ​The​ ​development​ ​of​ ​the​ ​model​ ​of​ ​the​ ​atom First:​ ​ ​atoms​ ​were​ ​thought​ ​to​ ​be​ ​tiny​ ​spheres​ ​that​ ​could​ ​not​ ​be​ ​divided Discovery​ ​of​ ​electron->​ ​plum​ ​pudding​ ​model​ ​(atom​ ​is​ ​a​ ​ball​ ​of​ ​positive​ ​charge​ ​with negative​ ​electrons​ ​embedded​ ​in​ ​it) Alpha​ ​particle​ ​scattering​ ​experiment->​ ​conclusion​ ​that​ ​the​ ​mass​ ​of​ ​an​ ​atom​ ​was concentrated​ ​at​ ​the​ ​centre​ ​(nucleus)​ ​and​ ​that​ ​the​ ​nucleus​ ​was​ ​charged Scattering​ ​experiment: A​ ​beam​ ​of​ ​alpha​ ​particles​ ​was​ ​aimed​ ​at​ ​very​ ​thin​ ​gold​ ​foil​ ​and​ ​their​ ​passage through​ ​was​ ​detected Some​ ​of​ ​the​ ​alpha​ ​particles​ ​emerged​ ​from​ ​the​ ​foil​ ​at​ ​different​ ​angles,​ ​and​ ​some even​ ​came​ ​straight​ ​back the​ ​positively​ ​charged​ ​alpha​ ​particles​ ​were​ ​being​ ​repelled​ ​and​ ​deflected​ ​by​ ​a small​ ​concentration​ ​of​ ​positive​ ​charge​ ​in​ ​the​ ​atom​ ​(nucleus) Neil​ ​Bohr:​ ​suggested​ ​electrons​ ​orbit​ ​the​ ​nucleus​ ​at​ ​specific​ ​distances​ ​(supported​ ​by experimental​ ​data) www.pmt.education  Later​ ​experiments:​ ​positive​ ​charge​ ​of​ ​any​ ​nucleus​ ​could​ ​be​ ​subdivided​ ​into​ ​a​ ​whole number​ ​of​ ​smaller​ ​particles,​ ​each​ ​particle​ ​having​ ​the​ ​same​ ​amount​ ​of​ ​positive​ ​charge (protons) James​ ​Chadwick’s​ ​work:​ ​ ​provided​ ​the​ ​evidence​ ​to​ ​show​ ​the​ ​existence​ ​of​ ​neutrons within​ ​the​ ​nucleus​ ​(had​ ​been​ ​an​ ​accepted​ ​scientific​ ​idea​ ​for​ ​about​ ​20​ ​years​ ​already) ​ ​Relative​ ​electrical​ ​charges​ ​of​ ​subatomic​ ​particles atomic​ ​number:​ ​the​ ​number​ ​of​ ​protons​ ​in​ ​an​ ​atom​ ​of​ ​an​ ​element. All​ ​atoms​ ​of​ ​a​ ​particular​ ​element​ ​have​ ​the​ ​same​ ​number​ ​of​ ​protons. Atoms​ ​of​ ​different​ ​elements​ ​have​ ​different​ ​numbers​ ​of​ ​protons. particle Relative​ ​charge proton +1 neutron 0 electron -1 An​ ​atom​ ​has​ ​an​ ​overall​ ​charge​ ​of​ ​0,​ ​so​ ​number​ ​of​ ​protons​ ​=​ ​number​ ​of​ ​electrons Size​ ​and​ ​mass​ ​of​ ​atoms Atoms​ ​are​ ​very​ ​small​ ​(​ ​radius​ ​of​ ​about​ ​0.1​ ​nm​ ​)​ ​and​ ​the​ ​radius​ ​of​ ​a​ ​nucleus​ ​is​ ​less​ ​than 1/10,000​ ​of​ ​that​ ​of​ ​the​ ​atom,​ ​though​ ​it​ ​holds​ ​almost​ ​all​ ​of​ ​the​ ​mass particle Relative​ ​mass proton 1 neutron 1 electron Very​ ​small Mass​ ​number:​ ​the​ ​sum​ ​of​ ​the​ ​protons​ ​and​ ​neutrons​ ​in​ ​an​ ​atom Isotopes:​ ​atoms​ ​of​ ​the​ ​same​ ​element​ ​with​ ​different​ ​numbers​ ​of​ ​neutrons This​ ​is​ h ​ ow​ ​atoms​ ​are​ ​shown​ ​in​ ​the​ ​periodic​ ​table: Relative​ ​atomic​ ​mass Relative​ ​atomic​ ​mass:​ ​ ​an​ ​average value​ ​that​ ​takes​ ​account​ ​of​ ​the​ ​abundance​ ​of the​ ​isotopes​ ​of​ ​the​ ​element www.pmt.education  Example​ ​question:​ ​carbon​ ​has​ ​2​ ​isotopes:​ ​carbon-14​​ ​with​ ​abundance​ ​20%​​ ​and carbon-12​ ​with​ ​abundance​ ​80%.​​ ​Calculate​ ​the​ ​relative​ ​atomic​ ​mass​ ​of​ ​carbon. To​ ​calculate​ ​it:​ ​((​isotope​ ​1​ ​mass​ ​x​ ​abundance)​ ​+​ ​(​isotope​ ​2​ ​mass​ ​x​ ​abundance))​ ​÷​ ​100 For​ ​this​ ​question:​ ​((​14​ ​x​ ​20​)​ ​+​ ​(​12​ ​x​ ​80​))​ ​÷​ ​100​ ​=​ ​1240​ ​÷​ ​100​ ​=​ ​12.4 Electronic​ ​structure electrons​ ​occupy​ ​the​ ​lowest​ ​available​ ​energy​ ​levels​ ​(the​ ​shells​ ​closest​ ​to​ ​the​ ​central nucleus) Electronic​ ​structure​ ​of​ ​an​ ​atom​ ​tells​ ​you​ ​how​ ​many​ ​electrons​ ​are​ ​in​ ​each​ ​shell e.g.​ ​for​ ​sodium:​ ​2​ ​electrons​ ​in​ ​shell​ ​1​ ​(closest​ ​to​ ​nucleus),​ ​8​ ​in​ ​shell​ ​2,​ ​1​ ​in​ ​shell​ ​3 Electronic​ ​structure=​ ​2,8,1​ ​or www.pmt.education