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ERSC 1F90 (47)
Dale Hess (4)
Lecture 2

earth science lecture 2 chemistry

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Brock University
Earth Sciences
Dale Hess

ABriefReviewOfChemistry Monday,September 19, 2011 7:22PM "AllThingsAreMadeof Atom"- Richard Feynman Atoms • Buildingblocksofallmatter To be more precise: -24 An atomic mass of 1u = 1.67262158 × 10 grams An electron has 0.05% of the mass of a proton. (20 electrons would have 1% of the mass of a proton). To be more precise: -24 An atomic mass of 1u = 1.67262158 × 10 grams An electron has 0.05% of the mass of a proton. (20 electrons would have 1% of the mass of a proton). Aproton has a mass equal to 99.8% of a neutron. • Thenumberofelectronsequalsthenumberofprotonsinanatom’snucleus(theirchargesbalancesothattheyareelectricallyneutral). ElectricalCharge 6protons - +6 6neutrons - 0 6electrons - -6 Netcharge-0 • Electronsoccurinspherical"shells"aboutthenucleus. • Ashellisaparticularregionwhereelectronsaremostlikelytobeatagiveninstantintimeastheorbitsarenot simpleasshownbelow • Electronshellsarealsotermed"energylevels"andeachcontainsaspecificnumberofelectrons • Whenelectronsareaddedorlost,theatomis nolongerneutral,ithasa chargethat iseitherpositiveornegative • Suchchargedatomsare termedIONS Neutralatom: Numberofprotons(+)equaltonumberofelectrons(-) (netcharge is0) Positiveion(Cation): number of protons (+) is greater thannumber of electrons (-) (netcharge is +, ion has a positive charge Negativeion(Anion): numberofprotons(+)islessthannumberofelectrons(-) (netchargeis-,ionhas anegativecharge) • Anatomof sodium(Na)has11 protons,11neutronsand11 electrons;2electronsintheinnershell,8fillingthe2 shellandoneelectroninthe valenceshell. nd • Thesodiumatommaylosethevalenceelectronsothatitsoutermostshell(the2 shell)isfull Thiscreatesasodiumionwhichhasa singlepositivechargeduetothefactthatit has onemoreprotonthan ithas electrons.(Thisionisgiventhe symbolNa .) ELEMENTS • Element:Thesimplestkindofchemical;itcannotbebrokendownintosimplerformsbyanyphysicalorchemicalprocess. • Atomsarethesmallestparticleofanelementthatretainsthecharacteristicsoftheelement. • Elementsaredefinedbythenumberofprotonsinthenucleioftheiratoms. • AtomicNumber:totalnumberofprotonsinthenucleusoftheatomsofan element. • Definestheelement;ifatomicnumberchangesthentheelementchanges. • Atomicmass(orweight):totalmassofallprotonsandneutrons(electronshavenegligiblemass) Notation 16 8O O= oxygen 8=atomicnumber(8protons) 16=atomicmass (8protons+ 8neutrons=16) PeriodicTable:thelistofallknownelementsinorderofincreasingatomicnumber. • AsofJuly2006 116 element
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