Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download File
Document related concepts
Transcript
10-11-16 • Whatisthebasicstructureoftheatomaswe knowittoday?Describethepartsofanatom withasmuchdetailasyoucan... Chapter4 EarlyTheoriesofMaAer Democritus(400-370BC)–firstto proposethatmaAernotinfinitelydivisible. • BelievedmaAermadeofparFcleshecalled “atomos”. • MaAercomposedofemptyspacethrough whichatomsmove. • AtomsindestrucFbleandindivisible. EarlyTheoriesofMaAer JohnDalton(1766-1844)–school teacherandscienFst. • Dalton’satomictheorybasedonDemocritus’s ideas. • AllmaAermadeofsmallparFclescalledatoms. • AtomsofagivenelementareidenFcal. EarlyTheoriesofMaAer Daltonalsopostulatedthat: • Atomscannotbecreated,destroyed ordividedintosmallerpieces. • AtomscancombineinwholenumberraFos. • Inchemicalrxns,atomsareseparated, combinedorrearranged. DefiningtheAtom • Atom:ThesmallestparFcleofanelement thatretainstheproperFesoftheelement. • BecauseofDalton’satomictheory,most scienFstsin1800sbelievedthattheatomwas likeaFnysolidballthatcouldnotbebroken upintoparts. • NowknowthattheatomisNOTindestrucFble orindivisible(subatomicparFcles) EarlyExperimentstoDescribetheAtom • J.J.Thomsonusedcathoderaytube tostudyatoms. • Showedthatthereweresmaller parFclesinatoms.ThoseparFcles latercametobeknownaselectrons. • LaterEugeneGoldsteinfound parFclesflowinginother direcFon.FirstindicaFonof posiFveparFcles(protons). J.J.Thomson CathodeRayTube TheAtomaround1900 • Theprevailingtheory wasthatofthe“plum pudding”model,put forwardbyJ.J.Thomson. • ItfeaturedaposiFve sphereofmaAerwith negaFveelectrons imbeddedinit. DiscoveryoftheNucleus • ErnestRutherford shotαparFcles atathinsheetof goldfoiland observedthe paAernofscaAer oftheparFcles. DiscoveryoftheNucleus DiscoveryoftheNucleus • SincesomeparFcles weredeflectedatlarge angles,Thomson’s model(plumpudding model)couldnotbe correct. TheNuclearAtom • Rutherfordpostulatedaverysmall,dense nucleuswiththeelectronsaroundthe outsideoftheatom. • Mostofthevolumeoftheatomisempty space. AtomicComposiFon–WhatWeKnow Theatomismostlyemptyspace • Protonsandneutronsinthenucleus. • Numberofelectronsisequaltothe numberofprotons. • Electronsfoundinspace aroundthenucleus.
